hi guys ! i found the quote referring to joni and warren. i too have the book by leonore fleischer mentioned in sylvia's post, oddly enough the quote i found actually mentions said book as it source. the quote is in brian hinton's book " joni mitchell: both sides now." the quote is on page 138, the last paragraph:
"in leonore fleischer's book, affairs are hinted at - never confirmed - with steven stills, leonard cohen, neil young, and warren beatty, who is rumored to be the inspiration for mitchell's ' coyote,' as he was for carly simon's 'you're so vain.' i promised a quote and by god a quote you will get. although it isn't exactly proof it is confirmation that it probably is so ? ( and that's the truth !) feeling dirty and cheap after having passed on that rumour, warren keith