6Wheeler M M,Feghall I. Much Ado about Nothing:Preservice Elementanry School Teachers'Concept of Zero[J].Joural for Research in Mathematics Education, 1983,14(3) :147-155.
7Eves H. An Introduction to the History of Mathematics[M].New York:CBS College Publishing, 1983.5-19.
8O' Connopr J J, Roberts E F. A History of Zero[EB/OL].(2000 - 11 - 08) ( 2006 - 07 - 20). http://www - groups, dcs.st - st - and. ac. uk/-history/ PrintHT/Zero. html.
