supported by the grant LSS (Grant No. 344.2008.1);the SB RAS Integration Grant (GrantNo. 2006.1.9) (Russia);National Natural Science Foundation of China (Grant No. 10771077);Natural Science Foundation of Guangdong Province (Grant No. 06025062)
The concept of Hall words was first introduced by P. Hall in 1933 in his investigation on groups of prime power order. Then M. Hall in 1950 showed that the Hall words form a basis of a free Lie algebra by using direct...