Friedman, Harvey M. Enormous Integers In Real Life(PDF). Ohio State University. 1 June 2000 [8 August 2017]. (原始内容存档(PDF)于2016-10-18).
Friedman, Harvey M. Long Finite Sequences(PDF). Ohio State University Department of Mathematics: 5, 48 (Thm.6.8). 8 October 1998 [8 August 2017]. (原始内容存档(PDF)于2017-08-09).
web.archive.org
TREE sequence. Googology Wiki | Fandom. [9 July 2020]. (原始内容存档于2020-01-09).
Friedman, Harvey M. Enormous Integers In Real Life(PDF). Ohio State University. 1 June 2000 [8 August 2017]. (原始内容存档(PDF)于2016-10-18).
Friedman, Harvey M. Long Finite Sequences(PDF). Ohio State University Department of Mathematics: 5, 48 (Thm.6.8). 8 October 1998 [8 August 2017]. (原始内容存档(PDF)于2017-08-09).
wikia.org
googology.wikia.org
TREE sequence. Googology Wiki | Fandom. [9 July 2020]. (原始内容存档于2020-01-09).