псы в рапиде » from archive
Википедия рулит. http://en.wikipedia.org/wiki/Cardinality There are two approaches to cardinality – one which compares sets directly using bijections and injections, and another which uses cardinal numbers.[1]
http://en.wikipedia.org/wiki/Cardinal_number Cardinality is defined in terms of bijective functions. ‎- псы в рапиде