Reference this Research Paper (copy & paste below code):
Longe I.O., Olupitan G.O., Ekundayo O.S. (2018); Cardinality of an Elementary Countably Infinite Set.;
Int J Sci Res Publ 4(7) (ISSN: 2250-3153). http://www.ijsrp.org/research-paper-0714.php?rp=P312888
