海量图书期刊资源，随时随地畅享阅读乐趣
Width of elements in free groupsR. I. Grigorchuk; P. F. Kurchanov · Ukrainian Mathematical Journal · 1991
Classification of epimorphisms of fundamental groups of surfaces onto free groupsR. I. Grigorchuk; P. F. Kurchanov · Mathematical Notes · 1990