ケーニヒの補題
↑ Note that, although Kőnig's name is properly spelled with a double acute accent, the lemma named after him is customarily spelled with an umlaut.
↑ Brouwer, L. E. J. (1927). "On the Domains of Definition of Functions", published in Jean van Heijenoort, editor, From Frege to Gödel, 1967.
Cenzer, D. (1999). " Π 1 0 {\displaystyle \Pi _{1}^{0}} classes in recursion theory". Handbook of Computability Theory. Elsevier. pp. 37–85. ISBN 0444898824。
König, D. (1926年). “Sur les correspondances multivoques des ensembles”. Fundamenta Mathematicae, (8): pp. 114–134. http://matwbn.icm.edu.pl/ksiazki/fm/fm8/fm815.