\providecommand{\bysame}{\leavevmode\hbox to3em{\hrulefill}\thinspace} \providecommand{\MR}{\relax\ifhmode\unskip\space\fi MR } % \MRhref is called by the amsart/book/proc definition of \MR. \providecommand{\MRhref}[2]{% \href{http://www.ams.org/mathscinet-getitem?mr=#1}{#2} } \providecommand{\href}[2]{#2} \begin{thebibliography}{1} \bibitem{b} N.~Bourbaki, \emph{Algebra {I}. {C}hapters 1--3}, Elements of Mathematics (Berlin), Springer-Verlag, Berlin, 1998, Translated from the French, Reprint of the 1989 English translation [ MR0979982 (90d:00002)]. \bibitem{f} J.B. Fraleigh, \emph{A {F}irst {C}ourse in {A}bstract {A}lgebra, {S}eventh {E}dition}, Addison {W}esley, Boston, 2003. \bibitem{g} J.A. Gallian, \emph{Contemporary {A}bstract {A}lgebra, {T}hird {E}dition}, D.C. Heath, Toronto, 1994. \bibitem{groth} Alexander Grothendieck, \emph{Cohomologie locale des faisceaux coh\'erents et th\'eor\`emes de {L}efschetz locaux et globaux ({SGA} 2)}, Documents Math\'ematiques (Paris) [Mathematical Documents (Paris)], 4, Soci\'et\'e Math\'ematique de France, Paris, 2005, S\'eminaire de G\'eom\'etrie Alg\'ebrique du Bois Marie, 1962, Augment\'e d'un expos\'e de Mich\`ele Raynaud. [With an expos\'e by Mich\`ele Raynaud], With a preface and edited by Yves Laszlo, Revised reprint of the 1968 French original. \MR{MR2171939 (2006f:14004)} \end{thebibliography}