RT Journal Article SR Electronic T1 Retinoic acid induced chordomas as a model of differential therapy JF Saudi Medical Journal JO Saudi Med J FD Prince Sultan Military Medical City SP 1236 OP 1237 VO 30 IS 9 A1 Bayrak, Omer F. A1 Aydemir, Esra A1 Sahin, Fikrettin YR 2009 UL http://smj.org.sa/content/30/9/1236.abstract AB