Robin Lakoff is one of the so-called "first generation" of linguists to look at women's speech as being quantitatively different from men's speech, and also one of the first generation of feminists to look towards linguistics as a scientific study to which to prove inherent sexism in language.  Although this text is dated (1975), it does serve as a key cited secondary reference for many of the articles published recently about gender and discourse.  Even other linguists who go on to refute Lakoff's dichotomies continue to cite her work regularly.  For my purposes, I may choose to quote from part 2 of her book "Why Women are Ladies" which deals with forms of politeness and how women specifically express politeness in speech, topics which I feel are still relevant today on the internet.