A first course of homological algebra [by] D. G. Northcott. Northcott, D. G. (Douglas Geoffrey) Algebra, Homological. QA169 .N67 512 NOF Bibliography: p. 203. Cambridge [Eng.] University Press 1973 1973 1973 Text xi, 205 p. http://www.loc.gov/catdir/enhancements/fy0901/72097873-d.html http://www.loc.gov/catdir/enhancements/fy0901/72097873-t.html eng