1. Wuts P.G.M., Kelly R.C.; US Patent No. 6,057,452; May 2, 2000; Assigned to Pharmacia and Upjohn Company
2. Haugwitz R.D. et al.; US Patent No. 4,942,184; July 17, 1990; Assigned: USA as represented by the Department of Health and Human Services, Washington, D.C.
3. Stella V.J., Mathew A.E.; US Patent No. 4,960,790; Octouber 2, 1990; Assigned: University of Kansas, Lawrence, Kans
4. Shinal E.C.; US Patent No. 6,160,165; Dec. 12, 2000; Assigned: Aesgen, Inc., Princeton
5. Merck Index 6870