In Chapters VI and VII several results are generalized, and there are indica-
tions of simplifications of proofs compared to the existing literature.
To follow the presentation, at least for the later chapters, I think that the reader
should have some familiarity with the basic structure theory of semisimple. Lie
groups and Lie algebras. After each chapter I have included some very brief notes
indicating related results, historical aspects or references to proofs not mentioned
in the text.