The American historian of German descent[20] Richard Blanke in his book Orphans of Versailles names several reasons for the exodus of the German population. The author has been criticised by Christian Raitz von Frentz and his book classified by him as part of a series on the subject that have an anti-Polish bias[21] Polish professor A. Cienciala says that Blanke's views in the book are sympathetic to Germany[22]