I guess you don't get out much, Anon. Here is a sampling of respectable online sources. Doing a bit of Google research yourself will turn up many, many more. The American Heritage Dictionary : Grammarians have sometimes objected to the so-called double genitive construction, as in a friend of...
ESL General English Grammar Questions
by
Mister Micawber
2 yr 197 days ago
Grammar, Conversations, Possessives, Constructions, Nouns, Pronouns, Whom, Idioms, Apostrophes, Genitives, Hyperboles