Embryonic Stem Cells Form Articular Cartilage, not Teratomas, in Osteochondral Defects of Rat Joints oleh Shigeyuki Wakitani, Hideyuki Aoki, Yasuji Harada, Masato Sonobe, Yusuke Morita, Ying Mu, Naohide Tomita, Yukio Nakamura, Satoshi Takeda, Takeshi K. Watanabe, Akira Tanigami