(EN) Ronald L. Graham, Donald E. Knuth e Oren Patashnik, Concrete Mathematics: A Foundation for Computer Science, 1989, ISSN 9780201142365 (WC · ACNP), OCLC17649857.
wikidata.org
(EN) Eric W. Weisstein, Fattoriale crescente, in MathWorld, Wolfram Research.
worldcat.org
(EN) Ronald L. Graham, Donald E. Knuth e Oren Patashnik, Concrete Mathematics: A Foundation for Computer Science, 1989, ISSN 9780201142365 (WC · ACNP), OCLC17649857.