http://www.keithschwarz.com
https://pl.wikipedia.org/wiki/Silniowy_system_pozycyjny
https://en.wikipedia.org/wiki/Factorial_number_system
https://en.wikipedia.org/wiki/Factorial_number_systemhttps://msdn.microsoft.com/en-us/library/aa302371.aspx
http://www.math.upenn.edu/~ted/210F10/References/Secretary.pdf
http://www.mimuw.edu.pl/~jrad/asd/inwersje.pdfhttps://pl.wikipedia.org/wiki/Systemy_pozycyjnehttps://en.wikipedia.org/wiki/Lehmer_code
http://www.keithschwarz.com/interesting/code/?dir=factoradic-permutation
http://www.oi.edu.pl/static/ attachment/20130203/1994.pdf - paragraf 7.3.1.