Free tools used for this website

I would like to thank everyone who composed the chess problems featured in my website,
as well as the programmers of the tools that i'm using:

Chess database and PGN viewer
with Stockfish chess engine:
PGN ChessBook

Copy chess diagrams from one program
or web page to another quickly and easily:

Ultra fast duplicate file finder/remover:
Yet Another Duplicate File Remover

Here you can find a vast chess problem database
which includes the solutions, some information about the composers,
the year they were first appeared and where they were published.
Yet Another Chess Problem Database