Millennium 3D chess

Millennium 3D chess is a three-dimensional chess variant created by William L. d'Agostino in 2001 which employs three vertically stacked 8×8 boards, with each player controlling a standard set of chess pieces. The inventor describes his objective as "extending the traditional chess game into a multilevel environment without distorting the basic game."
Rules.
Millennium 3‑D Chess rules extend the traditional (two-dimensional) chess game into a multi-level environment.
For notation purposes, the three board levels are denoted "1", "2" (the middle board), and "3". Moves are recorded in the same manner as chess, using algebraic notation, with the only difference that each square is prefaced by its level number. The white and black armies begin, in standard formation, on boards 1 and 3 respectively.
All pieces can always move as normal while staying on the same board. Additionally, every piece is able to move between boards. Each piece's additional permitted movement in the third dimension is extended from its conventional 2‑D movement as follows:
Example game.
George Davis vs. William d'Agostino, corr. 2006: 
References.
Bibliography