High-Tc superconductivity induced by doping rare-earth elements into CaFeAsF Peng Cheng, Bing Shen, Gang Mu, Xiyu Zhu, Fei Han, Bin Zeng and Hai-Hu Wen EPL, 85 6 (2009) 67003 Published online: 01 April 2009 DOI: 10.1209/0295-5075/85/67003