http://benji3up2kxewkqfcq7buxk2xd6zwy3zggnurkrm3l4cvwy2iipvyyad.onion/mirrors/gmpdoc/References.html
Arnold Schönhage and Volker Strassen, “Schnelle Multiplikation grosser
Zahlen”, Computing 7, 1971, pp. 281-292. Kenneth Weber, “The accelerated integer GCD algorithm”,
ACM Transactions on Mathematical Software,
volume 21, number 1, March 1995, pp. 111-122.