Richardson, L.F. (1911) The Approximate Arithmetical Solution by Finite Differences of Physical Problems Involving Differential Equations with an Application to the Stress in a Masonry Dam. Philosophical Transactions of the Royal Society of London. Series A, 210, 307-357.
 Polyanin, A.D. and Manzhirov, A.V. (2008) Handbook of Integral Equations. Chapman & Hall/CRC Press, Boca Raton and London.