It is difficult to ascertain how much of the Prayer Book is Cranmer's personal composition. Generations of liturgical scholars have been able to track down the sources that he used, including the Sarum Rite, writings from Hermann von Wied, and several Lutheran sources including Osiander and Justus Jonas. More problematic is determining how Cranmer worked on the book and with whom he worked. Despite the lack of knowledge of who might have helped him, he is given the credit for the editorship and the overall structure of the book.