ChemAxonFryer, R.I., Schmidt, R.A. and Sternbach, L.H.; U.S. Patent 3,100,770; August 13, 1963; assigned to Hoffmann-LaRoche Inc. Fryer, R.I., Schmidt, R.A. and Sternbach, L.H.; U.S. Patent 3,182,065; May 4, 1965; assigned to Hoffmann-LaRoche Inc. Fryer, R.I., Schmidt, R.A. and Sternbach, L.H.; US. Patent 3,182,067; May 4, 1965; assigned to Hoffmann-LaRoche Inc.