The book was published by a third party in 1991 but the author died in 1988. It's believed Elisabeth Schwarz, his wife contacted the publishing company to publish his book or had a will with the publishing agency to transfer ownership but currently there is no proof of that heavily implied the publisher may be infinging on the copyright of the author and if that was the case then there may be no enforcement of current copyright. On the publisher website 'nagel-kimch' , it's not even listed even in an advanced search