I have a question about a public domain self-help book that has lapsed copyrights in the USA and has been in the public domain for a few decades.
The organization is still in operation and they trademarked the name of the book and its abbreviation.
I'm the author of one mobile app of this self-help book in which the entire book is published along with the book title and its abbreviation in many places. The organization has now asked me to remove the name and its abbreviation from my app.
My question is, is it even possible to trademark the name of a public domain book?