C. Jeppsson, H. Saveland, U. Rydholm, and P. A. Berg, “OP-1 for cervical spine fusion: Bridging bone in only 1 of 4 rheumatoid patients but prednisolone did not inhibit bone induction in rats”, ActaO, vol. 70, no. 6, pp. 559–563, Jan. 1999.