1. Partial differential equations
2. E. W. Hobson, The Theory of Functions of a Real Variable and the Theory of Fourier Series, Vol. 2, Cambridge University Press, Cambridge, 1926, 702–710
3. An Elliptic Eigenvalue Problem for a Reentrant Region
4. E. C. Titchmarsh, The Theory of Functions, Oxford University Press, Oxford, 1939, 410–