1. Clark RL. letter to Dr. T. S. Painter, 11 February 1946 (McGovern Historical Center, Texas Medical Center MS 070. Series I. Box 11; File 3).
2. Clark RL. letter to Dr. O.T. (Jim) Claggett, Mayo Clinic, 26 March 1946 (McGovern Historical Center, Texas Medical Center MS 070. Series I. Box 11; file 3).
3. Clark RL. letter to Dr. Alton Ochsner, Ochsner Clinic, New Orleans, LA, 1 April 1946 (McGovern Historical Center, Texas Medical Center MS 070. Series I. Box 11; file 3)
4. Clark RL letter to Dr. Alton Ochsner, Ochsner Clinic, New Orleans, LA, 30 April 1946 (McGovern Historical Center, Texas Medical Center MS 070. Series I. Box 11; File 3).
5. Clark RL. letter to Dr. Alfred Shands, Dupont Institute, Wilmington, DE, 3 May 1946 (McGovern Historical Center, Texas Medical Center MS 070. Series II. Box 7; file 4).