The formation and carrying out of a plan of action is the main task in the course of the process of the chess struggle. Peter Romanovsky, Chess Middlegame Planning
To play the Slav successfully as Black demands considerable tenacity, robust defensive abilities and a healthy confidence in one's all-round skills. Graham Burgess, The Slav
In general the popularity of chess openings does, over time, bear a reasonable relationship to their objective merits. Peter Wells, Winning With The Trompowsky
When an enemy king is stuck in the centre, do everything possible to rip open central lines. These act as highways for your pieces, and allow them to make quick progress into the opponent's position. Jeremy Silman, The Reassess Your Chess Workbook
The critical examination of a position requires a consideration of many factors, but those concerning the pawn-structure usually deserve priority. Hans Kmoch, Pawn Power In Chess
One useful way of acquiring new ideas in the Closed Sicilian is to study the English Opening. That may sound a little odd, but 1.c4 e5 2.Nc3 Nc6 3.g3 g6 4.Bg2 Bg7 5.d3 d6 is a reversed Closed Sicilian. Richard Palliser, Starting Out: Closed Sicilian