Casti, J. <https://pure.iiasa.ac.at/view/iiasa/1179.html>  (2007).  Gregory Chaitin: Mathematician, Philosopher, and Friend.    In:  Randomness and Complexity, From Leibniz to Chaitin. Eds. Calude, C.S., pp. 417-420 World Scientific Publishing Co..  ISBN 978-981277083-7;9812770828;978-981277082-0 10.1142/9789812770837_0025 <https://doi.org/10.1142/9789812770837_0025>.