Chess endgame literature refers to books and magazines about chess endgames. Theory on the middlegame is less developed than the opening or endgames. Rook endings are probably the deepest and most well studied endgames. In 1634 Alessandro Salvio analyzed endgames, including a key position in rook endgames . The endgame database contained many six-piece endgames and five or fewer piece positions. The basic checkmates are types of pawnless endgames. This type of endgame is considered one of the more complex endgames. Positions with zugzwang occur fairly often in chess endgames, especially in king and pawn endgames. It turned out to be a manuscript detailing his lifetime work on rook endgames. Bishop and pawn endgames come in two distinctly different variants. This often occurs in king and pawn endgames. Grandmaster Ian Rogers summarized several of these endgames . Studying positions of reciprocal zugzwang is in the analysis of endgames. Here are some books on chess endgames in English. Lewis Stiller published a thesis with research on some six-piece tablebase endgames in 1995.