Hello Richard Wolke,
the book from Heinrich Hoehne is already out of print as I think. As it is written in German I'm afraid that it will not be easy to find it in American libaries. I've got a copy of it in my own. Wolke was a Zeller (a farmer) in Haustette, which belongs to Bakum, near Vechta. Now the name of the farm is "Große Siemer". In the book four pages deal with the name Wolke. I'll scan this pages and send it to your private e-mail-address.