Happy New Year! 10 new papers this time, from Anton, DavisDaniel, Harper (2) (that is John E. Harper of Notre Dame, not John Harper of Rochester), Hovey-Lockridge (2), Neusel (2), and Yagita (2). Mark Hovey New papers appearing on hopf between 11/29/07 and 1/18/08 1. http://hopf.math.purdue.edu/cgi-bin/generate?/Anton/homologicalSymbols Title: Homological symbols and the Quillen Conjecture Author(s): Marian F. Anton Abstract: We formulate a "correct" version of the Quillen conjecture on the cohomology of linear groups by defining an unstable form of Milnor K-theory and show that this version can be solved by a finite process. 2. http://hopf.math.purdue.edu/cgi-bin/generate?/DavisDaniel/fibrantmodel4 Title: Explicit fibrant replacement for discrete G-spectra Author: Daniel G. Davis Abstract: If C is the model category of simplicial presheaves on a site with enough points, with fibrations equal to the global fibrations, then it is well-known that the fibrant objects are, in general, mysterious. Thus, it is not surprising that, when G is a profinite group, the fibrant objects in the model category of discrete G-spectra are also difficult to get a handle on. However, with simplicial presheaves, it is possible to construct an explicit fibrant model for an object in C, under certain finiteness conditions. Similarly, in this paper, we show that if G has finite virtual cohomological dimension and X is a discrete G-spectrum, then there is an explicit fibrant model for X. Also, we give several applications of this concrete model related to closed subgroups of G. 3. http://hopf.math.purdue.edu/cgi-bin/generate?/Harper/modules-operads-monoidal Title: Homotopy theory of modules over operads and non-Sigma operads in monoidal model categories Author: John E. Harper Author's mailing address: Department of Mathematics, University of Notre Dame, Notre Dame, IN 46556, USA Comments: 49 pages, uses xy-pic; we have compiled the .tex file without using the better looking dvips,ps options in xy-pic, so the .dvi file should be device independent, but the diagrams may appear jagged etc. Abstract: This paper studies the existence of model category structures on modules and algebras over operads in monoidal model categories. 4. http://hopf.math.purdue.edu/cgi-bin/generate?/Harper/modules-spectra Title: Homotopy theory of modules over operads in symmetric spectra Author: John E. Harper Author's mailing address: Department of Mathematics, University of Notre Dame, Notre Dame, IN 46556, USA Comments: 21 pages, uses xy-pic; we have compiled the .tex file without using the better looking dvips,ps options in xy-pic, so the .dvi file should be device independent, but the diagrams may appear jagged etc. Abstract: This paper establishes model category structures on modules and algebras over operads in symmetric spectra, and studies when a morphism of operads induces a Quillen equivalence between corresponding categories of modules (resp. algebras) over operads. 5. http://hopf.math.purdue.edu/cgi-bin/generate?/Hovey-Lockridge/gen-gen-hyp The ghost dimension of a ring Mark Hovey Wesleyan University Keir Lockridge Wake Forest University We introduce the concept of the ghost dimension of a ring R. This is the longest nontrivial chain of maps in the derived category emanating from a perfect complex such that each map is zero on homology. We show that the ghost dimension of R is less than or equal to the weak dimension of R, with equality if R is coherent or has weak dimension 1. 6. http://hopf.math.purdue.edu/cgi-bin/generate?/Hovey-Lockridge/triproj Triangulations of Projective Modules Mark Hovey Wesleyan University Keir Lockridge Wake Forest University We show that the category of projective modules over a graded commutative ring admits a triangulation with respect to module suspension if and only if the ring is a finite product of graded fields and exterior algebras on one generator over a graded field (with a unit in the appropriate degree). We also classify the ungraded commutative rings for which the category of projective modules admits a triangulation with respect to the identity suspension. Applications to two analogues of the generating hypothesis in algebraic topology are given, and we translate our results into the setting of modules over a symmetric ring spectrum or $S$-algebra, where semisimple and von Neumann regular ring spectra are defined and discussed. 7. http://hopf.math.purdue.edu/cgi-bin/generate?/Neusel/hilbert Title: On the Hilbert Ideal Author: Mara D. Neusel Abstract: We prove the Hilbert number conjecture. 8. http://hopf.math.purdue.edu/cgi-bin/generate?/Neusel/schmid Title: Degree Bounds and the Regular Representation Author: Mara D. Neusel Abstract: This is a revised version of the paper with the same name posted during last summer. We prove Schmid's inequality in the general case, and Killius' conjecture for permutation representations. 9. http://hopf.math.purdue.edu/cgi-bin/generate?/Yagita/coniveaufilt Title: Coniveau filtration of cohomology of group Author: Nobuaki Yagita Abstract: We consider natural filtrations of mod p cohomology of a classifying space BG for a compact Lie group G, such that the reduced power operation preserves the filtration but the Bockstein opration descends the filtration degree one. An example of such filtrations is defined by the image from the motivic cohomology. For example, when BG=BO(n), this filtration coincides the coniveau filtration defined by Grothendieck. 10. http://hopf.math.purdue.edu/cgi-bin/generate?/Yagita/torsorEE Title: Note on Chow rings of nontrivial G-torsors over a field. Author: Nobuaki Yagita Abstract: Let G(k) be a split reductive group over a field k corresponding to a compact Lie group G. Let E be a nontrivial G(k)-torsor over a field k. In this paper we study the Chow ring of nontrivial G(k)-torsors E. For example when (G,p)=(F_4,3), we see that the positive degree of the mod 3 Chow ring of E is zero. ---------------- ---------------------------------------------- 4 new papers this time, from Blanc, Harper (again, this is John E. Harper of Notre Dame, not John Harper of Rochester), Kuhn, and Sati-Schreiber-Stasheff. Mark Hovey New papers appearing on hopf between 1/18/07 and 3/3/08 1. http://hopf.math.purdue.edu/cgi-bin/generate?/Blanc/quil Title: Generalized Andre-Quillen Cohomology Author: David Blanc Address: Dept. of Mathematics, U. Haifa, Haifa, Israel Abstract: We explain how the approach of Andre and Quillen to defining cohomology and homology as suitable derived functors extends to generalized (co)homology theories, and how this identification may be used to study the relationship between them. As a side benefit, we clarify exactly what assumptions on an (algebraic) category are needed in order for the approach of Beck and Andre-Quillen to work. We also show how the description may be applied to construct universal coefficient and reverse Adams spectral sequences. 2. http://hopf.math.purdue.edu/cgi-bin/generate?/Harper/QuillenHomology Title: Bar constructions and Quillen homology of modules over operads Author: John E. Harper Author's mailing address: Department of Mathematics, University of Notre Dame, Notre Dame, IN 46556, USA Comments: 33 pages, uses xy-pic; compiled the .tex file without using the dvips,ps options in xy-pic, to ensure .dvi is device independent, but diagrams may now appear jagged, etc. Abstract: This paper shows that Quillen derived homology of modules and algebras over an operad, for symmetric sequences of symmetric spectra and unbounded chain complexes, can be calculated using simplicial bar constructions, modulo cofibrancy conditions. Working with several model category structures, a homotopical proof is given, after showing that certain homotopy colimits in modules and algebras over an operad can be easily understood. The key result here, which is at the heart of this paper, is showing that the forgetful functor commutes with certain homotopy colimits. 3. http://hopf.math.purdue.edu/cgi-bin/generate?/Kuhn/telescopic Title: A guide to telescopic functors Author: Nicholas J. Kuhn Address: University of Virginia, Charlottesville, VA 22904 Abstract: In the mid 1980's, Pete Bousfield and I constructed certain p--local `telescopic' functors Phi_n from spaces to spectra, for each prime p and each positive integer n. These have striking properties that relate the chromatic approach to homotopy theory to infinite loopspace theory: roughly put, the spectrum Phi_n(Z) captures the v_n periodic homotopy of a space Z. Recently there have been a variety of new uses of these functors, suggesting that they have a central role to play in calculations of periodic phenomena. Here I offer a guide to their construction, characterization, application, and computation. 4. http://hopf.math.purdue.edu/cgi-bin/generate?/Sati-Schreiber-Stasheff/LCon Title: L-infinity algebra connections and applications to String- and Chern-Simons n-transport Authors: Hisham Sati, Urs Schreiber and Jim Stasheff Abstract: We give a generalization of the notion of a Cartan-Ehresmann connection from Lie algebras to L-infinity -algebras and use it to study the obstruction theory of lifts through higher String-like extensions of Lie algebras. We find (generalized) Chern-Simons and BF-theory functionals this way and describe aspects of their parallel transport and quantization. It is known that over a D-brane the Kalb-Ramond background field of the string restricts to a 2-bundle with connection (a gerbe) which can be seen as the obstruction to lifting the PU(H)-bundle on the D-brane to a U(H)-bundle. We discuss how this phenomenon generalizes from the ordinary central extension U(1) -> U(H) -> PU(H) to higher categorical central extensions, like the String-extension B U(1) -> String(G) -> G. Here the obstruction to the lift is a 3-bundle with connection (a 2-gerbe): the Chern-Simons 3-bundle classified by the first Pontrjagin class. For G = Spin(n) this obstructs the existence of a String-structure. We discuss how to describe this obstruction problem in terms of Lie n-algebras and their corresponding categorified Cartan-Ehresmann connections. Generalizations even beyond String- extensions are then straightforward. For G = Spin(n) the next step is "Fivebrane structures'' whose existence is obstructed by certain generalized Chern-Simons 7-bundles classified by the second Pontrjagin class. -------------------- ---------------------------------- My semester has ended, my daughter has chosen a college, and I finally have some time to deal with Hopf. Sorry for the long delay. 7 new papers this time, from Blanc-Johnson-Turner, Broto-Moller-Oliver, Carlson-Chebolu-Minac, Neusel-Sezer, Serikbaev-Bitibaeva-Yerzhanov-Myrazukulov, Yagita (2). Mark Hovey New papers appearing on hopf between 3/3/07 and 5/15/08 1. http://hopf.math.purdue.edu/cgi-bin/generate?/Blanc-Johnson-Turner/lgss Title: Local-to-global spectral sequences for the cohomology of diagrams Authors: David Blanc, Mark W. Johnson, and James M. Turner Address: Department of Mathematics, University of Haifa, 31905 Haifa, Israel Department of Mathematics, Penn State Altoona, Altoona, PA 16601, USA Department of Mathematics, Calvin College, Grand Rapids, MI 49546, USA Abstract: The cohomology of diagrams arises in various areas of mathematics, such as deformation theory, classifying diagrams of groups, and in homotopy theory, in the context of the rectification of homotopy-commutative diagrams, and thus in the study of higher homotopy and cohomology operations. For this purpose we construct ``local-to-global'' spectral sequences for the cohomology of a diagram, which can be used to compute the cohomology of the full diagram in terms of smaller pieces. We also explain why such a local-to-global approach is relevant to higher operations. 2. http://hopf.math.purdue.edu/cgi-bin/generate?/Broto-Moller-Oliver/bmo1 Authors: C. Broto, J. M. M\o{}ller, and B. Oliver Title: Equivalences between fusion systems of finite groups of Lie type Subject class: Primary 20D06, Secondary 55R37, 20D20 keywords: groups of Lie type, fusion systems, classifying spaces, p-completion Abstract: We prove, for certain pairs $G,G'$ of finite groups of Lie type, that the $p$-fusion systems $F_p(G)$ and $F_p(G')$ are equivalent. In other words, there is an isomorphism between a Sylow $p$-subgroup of $G$ and one of $G'$ which preserves $p$-fusion. This occurs, for example, when $G=\Gamma(q)$ and $G'=\Gamma(q')$ for a simple Lie ``type'' $\Gamma$, and $q$ and $q'$ are prime powers, both prime to $p$, which generate the same closed subgroup of $p$-adic units. Our proof uses homotopy theoretic properties of the $p$-completed classifying spaces of $G$ and $G'$, and we know of no purely algebraic proof of this result. 3. http://hopf.math.purdue.edu/cgi-bin/generate?/Carlson-Chebolu-Minac/fgt Finite generation of Tate cohomology Jon F. Carlson Department of Mathematics University of Georgia Athens, GA 30602, USA Sunil K. Chebolu Department of Mathematics University of Western Ontario London, ON N6A 5B7, Canada Jan Minac Department of Mathematics University of Western Ontario London, ON N6A 5B7, Canada Abstract: Let G be a finite group and let k be a field of characteristic p. If M is a finitely generated indecomposable non-projective kG-module, we conjecture that the Tate cohomology of G with coefficients in M is finitely generated over the Tate cohomology ring of G if and only if the support variety V_G(M) of M is equal to the entire maximal ideal spectrum V_G(k). We prove various results all of which support this conjecture. It is also shown that all finitely generated kG-modules over a group G have finitely generated Tate cohomology if and only if G has periodic cohomology. 4. http://hopf.math.purdue.edu/cgi-bin/generate?/Neusel-Sezer/separating TITLE: Characterizing Separating Invariants AUTHORS: Mara D.~Neusel and M\"uf\.it Sezer ABSTRACT: We study separating algebras for rings of invariants of finite groups. We give an algebraic characterization for these. Furthermore, we describe a particularly nice separating subalgebra for rings of invariants of p-groups in characteristic p. This leads to a characterization of subalgebras such that their p-root and integral closure is equal to the ring of invariants. Finally, we present separating sets for invariants rings of nonmodular representations of abelian groups whose size depends only on the degree of the representation. 5. http://hopf.math.purdue.edu/cgi-bin/generate?/Serikbaev-Bitibaeva-Yerzhanov-Myrazukulov/flow [Your moderator was in a quandary over this paper, which is clearly not remotely algebraic topology, but decided to err on the side of openness] Integrable isotropic geometrical flows and Heisenberg ferromagnets N.S.Serikbaev, Zh.M.Bitibaeva, K.K.Yerzhanov, R.Myrzakulov* Department of General and Theoretical Physics, Eurasian National University, Astana, 010008, Kazakhstan Abstract Geometrical Flows (GF) play an important role in modern mathematics and physics. In this letter we have considered some integrable isotropic GF Ricci Flows (RF) and mean curvature flows (MCF) ~ which are related with integrable Heisenberg ferromagnets. In 2+1 dimensions, these GF have a singularity at t = t0. 6. http://hopf.math.purdue.edu/cgi-bin/generate?/Yagita/motsplitG Title: Note on the mod p motivic cohomology of algebraic groups. Author: Nobuaki Yagita AMS classification numbers: 55P35, 57T25. Adress of Author: Faculty of Education, Ibaraki University, Ibaraki, Japan. Abstract: Let G_k be a split reductive group over a field k of ch(k)=0 corresponding to a compact Lie group G. In this paper, we show that the mod p motivic cohomology is isomorphic to the tensor product of the usual mod p cohomology H^*(G;Z/p) and the motivic cohomology H^{*,*'}(Spec(k);Z/p), when G=SO_n,G_2,F_4,E_6. We also give an example of nonsplit case (G=G_2,p=2,k=R) which does not hold the above isomorphism. 7. http://hopf.math.purdue.edu/cgi-bin/generate?/Yagita/realchow Title: Note on motivic cohomology of anisotropic real quadrics. Author: Nobuaki Yagita AMS classification numbers: 55P35, 57T25. Adress of Author: Faculty of Education, Ibaraki University, Ibaraki, Japan. Abstract: In this paper, we compute the mod 2 motivic cohomology H^{*,*'}(X;Z/2) for the anisotropic quadric X over R the field of real numbers. ----------- BABYL OPTIONS: -*- rmail -*- Version: 5 Labels: Note: This is the header of an rmail file. Note: If you are seeing it in rmail, Note: it means the file has no messages in it.  1, edited,, Mail-from: From dmd1@lehigh.edu Sat Jan 17 18:19:15 1998 Received: from nss4.cc.Lehigh.EDU (root@nss4.CC.Lehigh.EDU [128.180.1.13]) by mail.wesleyan.edu (8.8.6/8.7.3) with ESMTP id SAA10234 for ; Sat, 17 Jan 1998 18:20:52 -0500 (EST) Received: from ns4-1.CC.Lehigh.EDU (root@ns4-1.CC.Lehigh.EDU [128.180.1.42]) by nss4.cc.Lehigh.EDU (8.8.8/8.8.5) with ESMTP id SAA119110; Sat, 17 Jan 1998 18:23:02 -0500 Received: (from dmd1@localhost) by ns4-1.CC.Lehigh.EDU (8.8.5/8.8.5) id SAA39528; Sat, 17 Jan 1998 18:19:17 -0500 Message-Id: <199801172319.SAA39528@ns4-1.CC.Lehigh.EDU> Date: Sat, 17 Jan 1998 18:19:15 EST From: dmd1@lehigh.edu (DONALD M. DAVIS) X-Mailer: SENDM [Version 2.0.17] Subject: new Hopf listings To: Distribution.List@lehigh.edu (toplist) Content-Type: text X-UIDL: aacd4710beaa4a6483935a131ded8f1b Lines: 256 Xref: picard.math.wesleyan.edu davis:291 X-Gnus-Newsgroup: davis:291 Sun Jan 18 06:29:52 1998 *** EOOH *** Date: Sat, 17 Jan 1998 18:19:15 EST From: dmd1@lehigh.edu (DONALD M. DAVIS) Subject: new Hopf listings To: Distribution.List@lehigh.edu (toplist) Content-Type: text Xref: picard.math.wesleyan.edu davis:291 *** EOOH *** Date: Sat, 17 Jan 1998 18:19:15 EST From: dmd1@lehigh.edu (DONALD M. DAVIS) Subject: new Hopf listings To: Distribution.List@lehigh.edu (toplist) X-UIDL: aacd4710beaa4a6483935a131ded8f1b Xref: picard.math.wesleyan.edu davis:291 X-Gnus-Newsgroup: davis:291 Sun Jan 18 06:29:52 1998 My semester has ended, my daughter has chosen a college, and I finally have some time to deal with Hopf. Sorry for the long delay. 7 new papers this time, from Blanc-Johnson-Turner, Broto-Moller-Oliver, Carlson-Chebolu-Minac, Neusel-Sezer, Serikbaev-Bitibaeva-Yerzhanov-Myrazukulov, Yagita (2). Mark Hovey New papers appearing on hopf between 3/3/07 and 5/15/08 1. http://hopf.math.purdue.edu/cgi-bin/generate?/Blanc-Johnson-Turner/lgss Title: Local-to-global spectral sequences for the cohomology of diagrams Authors: David Blanc, Mark W. Johnson, and James M. Turner Address: Department of Mathematics, University of Haifa, 31905 Haifa, Israel Department of Mathematics, Penn State Altoona, Altoona, PA 16601, USA Department of Mathematics, Calvin College, Grand Rapids, MI 49546, USA Abstract: The cohomology of diagrams arises in various areas of mathematics, such as deformation theory, classifying diagrams of groups, and in homotopy theory, in the context of the rectification of homotopy-commutative diagrams, and thus in the study of higher homotopy and cohomology operations. For this purpose we construct ``local-to-global'' spectral sequences for the cohomology of a diagram, which can be used to compute the cohomology of the full diagram in terms of smaller pieces. We also explain why such a local-to-global approach is relevant to higher operations. 2. http://hopf.math.purdue.edu/cgi-bin/generate?/Broto-Moller-Oliver/bmo1 Authors: C. Broto, J. M. M\o{}ller, and B. Oliver Title: Equivalences between fusion systems of finite groups of Lie type Subject class: Primary 20D06, Secondary 55R37, 20D20 keywords: groups of Lie type, fusion systems, classifying spaces, p-completion Abstract: We prove, for certain pairs $G,G'$ of finite groups of Lie type, that the $p$-fusion systems $F_p(G)$ and $F_p(G')$ are equivalent. In other words, there is an isomorphism between a Sylow $p$-subgroup of $G$ and one of $G'$ which preserves $p$-fusion. This occurs, for example, when $G=\Gamma(q)$ and $G'=\Gamma(q')$ for a simple Lie ``type'' $\Gamma$, and $q$ and $q'$ are prime powers, both prime to $p$, which generate the same closed subgroup of $p$-adic units. Our proof uses homotopy theoretic properties of the $p$-completed classifying spaces of $G$ and $G'$, and we know of no purely algebraic proof of this result. 3. http://hopf.math.purdue.edu/cgi-bin/generate?/Carlson-Chebolu-Minac/fgt Finite generation of Tate cohomology Jon F. Carlson Department of Mathematics University of Georgia Athens, GA 30602, USA Sunil K. Chebolu Department of Mathematics University of Western Ontario London, ON N6A 5B7, Canada Jan Minac Department of Mathematics University of Western Ontario London, ON N6A 5B7, Canada Abstract: Let G be a finite group and let k be a field of characteristic p. If M is a finitely generated indecomposable non-projective kG-module, we conjecture that the Tate cohomology of G with coefficients in M is finitely generated over the Tate cohomology ring of G if and only if the support variety V_G(M) of M is equal to the entire maximal ideal spectrum V_G(k). We prove various results all of which support this conjecture. It is also shown that all finitely generated kG-modules over a group G have finitely generated Tate cohomology if and only if G has periodic cohomology. 4. http://hopf.math.purdue.edu/cgi-bin/generate?/Neusel-Sezer/separating TITLE: Characterizing Separating Invariants AUTHORS: Mara D.~Neusel and M\"uf\.it Sezer ABSTRACT: We study separating algebras for rings of invariants of finite groups. We give an algebraic characterization for these. Furthermore, we describe a particularly nice separating subalgebra for rings of invariants of p-groups in characteristic p. This leads to a characterization of subalgebras such that their p-root and integral closure is equal to the ring of invariants. Finally, we present separating sets for invariants rings of nonmodular representations of abelian groups whose size depends only on the degree of the representation. 5. http://hopf.math.purdue.edu/cgi-bin/generate?/Serikbaev-Bitibaeva-Yerzhanov-Myrazukulov/flow [Your moderator was in a quandary over this paper, which is clearly not remotely algebraic topology, but decided to err on the side of openness] Integrable isotropic geometrical flows and Heisenberg ferromagnets N.S.Serikbaev, Zh.M.Bitibaeva, K.K.Yerzhanov, R.Myrzakulov* Department of General and Theoretical Physics, Eurasian National University, Astana, 010008, Kazakhstan Abstract Geometrical Flows (GF) play an important role in modern mathematics and physics. In this letter we have considered some integrable isotropic GF Ricci Flows (RF) and mean curvature flows (MCF) ~ which are related with integrable Heisenberg ferromagnets. In 2+1 dimensions, these GF have a singularity at t = t0. 6. http://hopf.math.purdue.edu/cgi-bin/generate?/Yagita/motsplitG Title: Note on the mod p motivic cohomology of algebraic groups. Author: Nobuaki Yagita AMS classification numbers: 55P35, 57T25. Adress of Author: Faculty of Education, Ibaraki University, Ibaraki, Japan. Abstract: Let G_k be a split reductive group over a field k of ch(k)=0 corresponding to a compact Lie group G. In this paper, we show that the mod p motivic cohomology is isomorphic to the tensor product of the usual mod p cohomology H^*(G;Z/p) and the motivic cohomology H^{*,*'}(Spec(k);Z/p), when G=SO_n,G_2,F_4,E_6. We also give an example of nonsplit case (G=G_2,p=2,k=R) which does not hold the above isomorphism. 7. http://hopf.math.purdue.edu/cgi-bin/generate?/Yagita/realchow Title: Note on motivic cohomology of anisotropic real quadrics. Author: Nobuaki Yagita AMS classification numbers: 55P35, 57T25. Adress of Author: Faculty of Education, Ibaraki University, Ibaraki, Japan. Abstract: In this paper, we compute the mod 2 motivic cohomology H^{*,*'}(X;Z/2) for the anisotropic quadric X over R the field of real numbers. ---------------------Instructions----------------------------- To subscribe or unsubscribe to this listserv, go to https://lists.lehigh.edu/mailman/listinfo/algtop-l. To see past issues of new submissions to Hopf, go to http://math.wesleyan.edu/~mhovey/archive/ To get the papers listed above, go to the URL listed. The general Hopf archive URL is http://hopf.math.purdue.edu There is a web form for submitting papers to Hopf on this site as well. You should submit an abstract as well. Clarence has explicit instructions for the form of this abstract: see http://hopf.math.purdue.edu/new-html/submissions.html In particular, your abstract is meant to be read by humans, so should be as readable as possible. I reserve the right to edit unreadable abstracts. You should then e-mail Clarence at wilker at math.purdue.edu telling him what you have uploaded. The largest archive of math preprints is at http://arxiv.gov There is an algebraic topology section in this archive. The most useful way to browse it or submit papers to it is via the front end developed by Greg Kuperberg: http://front.math.ucdavis.edu To get the announcements of new papers in the algebraic topology section at the arXiv, send e-mail to math@arxiv.org with subject line "subscribe" (without quotes), and with the body of the message "add AT" (without quotes). I am solely responsible for these messages---don't send complaints about them to Clarence. Thanks to Clarence for creating and maintaining the archive.