Dufresne Jean. Sammlung leichterer Schachaufgaben Tom I

Malmö: Electronic Edition, 2000. — 106 p.
This edition is based on the edition published by Philipp Reclam jun.,Leipzig in 1881.All direct problems have been computer tested using Matthieu Leschemelle’so Problemiste v. 1.90. The studies have been checked using fritz 6 and Crafty, using the Nalimov endgame databases. The conditional problems, however, have only been checked for obvious errors.