Well there aren't that many to be honest, but there is at least one! I was looking through Google Books for any new references when I was slightly surprised to find a reference to a Yelf in an anthology of American Erotic stories called Best Fetish Erotica. The editor is Cara Bruce and the snippet that caught my eye was a reference to one of the heroines who
... lost her virginity to a sixty year old director, a vicious genius named Max Yelf the director of a troupe called Dollsbody. Yelf's mission was to drag theatre off the stage and into the streets...I think it's probably safe to assume that the sort of theatre Max Yelf had in mind wasn't Shakespeare or Chekov and possibly of a more burlesque character, but it will be interesting to see how well he succeeded.
From a family history point of view the choice of the name is quite interesting. This is an American anthology and there were few if any American Yelf's that might have served as a template. The Yelf name had turned up in earlier American fiction (mainly in the Kellog 'Ark Island' series of children's novels mentioned in a previous post) and there are some Canadian Yelf's of course, but I wonder if the choice of name was arbitrary - in that the author 'made it up' or whether there is some other family connection? All very intriguing...
The only course of action for me is to purchase the anthology, read the story and do my best to contact the author to see what information they can impart. Any responses I eventually obtain will, of course, appear on here but if you'll excuse me I have a collection of Erotic stories to purchase (Well it's a chore. but someone has to do it and research can be hell)