Often in the opening, if one player is aiming for the initiative, which he considers will be persistent and increasing, for the sake of this he may make positional weakenings or even sacrifice material. Alexey Suetin, Plan Like A Grandmaster
If a concrete plan of action, intended in the middlegame, requires the creation of backward, doubled, isolated and even a formation of (such) pawns, then it is necessary to go in for this by discarding abstract considerations relevant only to the endgame. Peter Romanovsky, Chess Middlegame Planning
Every idea deserves to be examined, but by no means all of them deserve to be carried out. Complicated logical constructs ought to be treated with suspicion, since they will all too often cause fresh problems to arise. Viacheslav Eingorn, Decison-Making At The Chessboard
An extra pawn can best be exploited in a pawn ending, or an ending with knights or like-coloured bishops. Luděk Pachman, Complete Chess Strategy 1: Planning The Pieces
[Comment after 1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.d3] Not aiming for an opening advantage. Only 4.0-0 gives chances of an advantage. Garry Kasparov, My Great Predecessors
The possessor of the isolated d pawn often employs the h pawn in his attack. Usually it happens when there is an enemy pawn on g6 (g3), which in this case attracts the h pawn like a magnet. Alexander Baburin, Winning Pawn Structures