1. L. Cagniard , 1939 . Reflexion et Refraction des Ondes Seismiques Progressives , Gauthier-Villars, Paris. An English translation and review entitled Reflection and Refraction of Progressive Seismic Waves has been written by E. A. Flinn and C. H. Dix, McGraw-Hill, New York, 1962 1962
2. E. Jahnke, and F. Emde , 1945, Tables of Functions , pp52 , 52 , 52 , Dover, New York.