great depth by serious players. "Novelties", or new, previously unexplored variations are often discovered and played by professional players. These new lines can refute lines that were previously thought to be sound. The games that represent this discovery process are represented in these ever-changing and expanding tables. With the advent of computer databases, even the most casual player can explore an opening line deeply, looking for novelties to spring on their opponents. Example External sources of chess opening theory tables John Nunn (Editor), Graham Burgess, John Emms, Joe Gallagher (1999), Nunn's Chess Openings. . Nick de Firmian, Walter Korn (1999), Modern Chess Openings: MCO-14. . Aleksandar Matanović, editor, Encyclopaedia of Chess Openings, 5 volumes (Belgrade: Šahovski informator) Chess opening theory table