By Gregory Karpilovsky
Allow N be a standard subgroup of a finite workforce G and allow F be a box. a big strategy for developing irreducible FG-modules contains the applying (perhaps repeated) of 3 simple operations: (i) restrict to FN. (ii) extension from FN. (iii) induction from FN. this can be the `Clifford conception' built via Clifford in 1937. long ago 20 years, the speculation has loved a interval of energetic improvement. the rules were bolstered and reorganized from new issues of view, in particular from the perspective of graded earrings and crossed items. the aim of this monograph is to tie jointly numerous threads of the improvement so as to supply a entire photo of the present country of the topic. it's assumed that the reader has had the identical of a typical first-year graduate algebra path, i.e. familiarity with simple ring-theoretic, number-theoretic and group-theoretic suggestions, and an figuring out of basic houses of modules, tensor items and fields.