%0 Journal Article
%A Zheng, Xizhong
%T On the hierarchies of $\Delta ^0_2$-real numbers
%J RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
%D 2007
%P 3-25
%V 41
%N 1
%I EDP-Sciences
%U http://www.numdam.org/articles/10.1051/ita:2007008/
%R 10.1051/ita:2007008
%G en
%F ITA_2007__41_1_3_0