[1] Zienkiewicz, O. C., Taylor, R. L. The Finite Element Method (Volume 1 - 3), Butterworth-Heinemann, Oxford 2000, ISBN 0-7506-5049-4
[2] Singiresu S. Rao. The Finite Element Method in Engineering. 5th edition, Elsevier 2011, doi:10.1016/B978-1-85617-661-3.00024-6