 Complete the following phrase:  Sometimes practical considerations are taken into account. In 1977 Viktor Korchnoi and former World Champion Tigran Petrosian played a twelve-game quarter-final Candidates Match to ultimately determine the challenger for the 1978 World Championship. After eleven games Korchnoi was leading by one point, so he only needed a draw in the final game to advance to the semi-finals. Korchnoi, as Black, was winning this game but he offered a draw after 40 moves. According to Edmar Mednis, it was gentlemanly and the practical thing to do . Korchnoi went on to unsuccessfully challenge Anatoly Karpov for the 