TY  - JOUR
AU  - Zheng, Xizhong
TI  - On the hierarchies of $\Delta ^0_2$-real numbers
JO  - RAIRO - Theoretical Informatics and Applications - Informatique Théorique et Applications
PY  - 2007
SP  - 3
EP  - 25
VL  - 41
IS  - 1
PB  - EDP-Sciences
UR  - http://www.numdam.org/articles/10.1051/ita:2007008/
DO  - 10.1051/ita:2007008
LA  - en
ID  - ITA_2007__41_1_3_0
ER  -