Complex sentence: Reprinted in the "Classics in mathematics" series, 2000; it studies van Kampen diagrams, corresponding to finite group presentations, via combinatorial curvature conditions and derives algebraic and algorithmic properties of groups from such analysis.
Split into simpler sentences: Reprinted in the "Classics in mathematics" series, 2000. It studies van Kampen diagrams, corresponding to finite group presentations, via combinatorial curvature conditions and derives algebraic and algorithmic properties of groups from such analysis.