** 'Lema lui Burnside':https://artofproblemsolving.com/wiki/index.php/Burnside%27s_Lemma
** 'Formula lui Cayley':https://goo.gl/2O1ruS
*** Probleme: 'zapezi2':problema/zapezi2

** 'Trecere de la combinare/permutare la indexul ei si invers':http://algopedia.ro/wiki/index.php/Clasele_11-12_lec%C8%9Bia_6_-_22_oct_2014#Codificarea_permut.C4.83rilor
*** Probleme: 'perm3':problema/perm3, 'perm5':problema/perm5, 'nkperm':problema/nkperm

* 'Mobius Function':https://www.quora.com/profile/Surya-Kiran/Posts/A-Dance-with-Mobius-Function
* Probabilitati
** 'Expected value':https://en.wikipedia.org/wiki/Expected_value: 'Tequila':problema/tequila, 'Sms':problema/sms, 'Expected Velea':problema/expected, 'Albume':problema/albume, 'Diapazon':problema/diapazon
** 'Ballot theorem':https://goo.gl/6kQZ8l
* 'Principiul includerii si excluderii':principiul-includerii-si-excluderii

** Probleme: 'cowfood':problema/cowfood, 'indep':problema/indep, 'frac':problema/frac, 'CF 451E':http://codeforces.com/contest/451/problem/E, 'light2':problema/light2, 'trickortreat':problema/trickortreat

** Probleme: 'cowfood':problema/cowfood, 'indep':problema/indep, 'frac':problema/frac, 'CF 451E':http://codeforces.com/contest/451/problem/E, 'light2':problema/light2,