Petko Petkov's chess archive

 QUOTE 
It has existed since 1958 and is constantly updated. It includes a large number of unpublished articles, originals, work schemes and suggestions for new fairy units. A central place in the archive is occupied by the computer version of my personal system (PAPGS), for theoretical and practical research and experiments and my own methods of composing. In principle I am never in a hurry with publication, but rather do the exact opposite – my problems stay for quite a long time in the archive and are repeatedly analysed looking for the optimal version.