1. Green, G., see Hydrodynamics. H. Lamb, § 43, § 58, Dover, 1954
2. Betti, E., see A Treatise on the Mathematical Theory of Elasticity. A.E. Love, § 121, Dover, 1944
3. Somigliana, C, see A.E. Love, loc. cit. § 169
4. Kirchhoff, G., see A.E. Love, loc. cit. § 210.
5. Baker, B.B. and Copson, E.T.,The Mathematical Theory of Huygens’s Principle. 2nd ed. Oxford Univ. Press, 1950