'Row echelon form':http://en.wikipedia.org/wiki/Row_echelon_form
Probleme:

'To xor or not to xor sgu':http://acm.sgu.ru/problem.php?contest=0&problem=275
'XOR campion':http://campion.edu.ro/problems/3/323/xor_ro.htm
'Puzzle sgu':http://acm.sgu.ru/problem.php?contest=0&problem=260
'Rational Resistors uva':http://online-judge.uva.es/p/v108/10808.html
'Extrapolation Using a Difference Table uva':http://online-judge.uva.es/p/v3/326.html
'Simple calculations uva':http://online-judge.uva.es/p/v100/10014.html
'BColor infoarena':http://infoarena.ro/problema/bcolor
'Laser infoarena':http://infoarena.ro/problema/laser
'XORing topcoder':http://www.topcoder.com/stat?c=problem_statement&pm=4829&rd=8095&rm=246636&cr=270505
'Escape the jail topcoder':http://www.topcoder.com/stat?c=problem_statement&pm=7353

'SGU 275 To xor or not to xor':http://acm.sgu.ru/problem.php?contest=0&problem=275
'.campion Xor':http://campion.edu.ro/problems/3/323/xor_ro.htm
'SGU 260 Puzzle':http://acm.sgu.ru/problem.php?contest=0&problem=260
'UVA 10808':http://online-judge.uva.es/p/v108/10808.html
'UVA 326':http://online-judge.uva.es/p/v3/326.html
'UVA 10014':http://online-judge.uva.es/p/v100/10014.html
'BColor':problema/bcolor
'Laser':problema/laser
'TC XORing':http://www.topcoder.com/stat?c=problem_statement&pm=4829&rd=8095&rm=246636&cr=270505
'TC Escape the jail':http://www.topcoder.com/stat?c=problem_statement&pm=7353

'Register CEOI 2003':http://ceoi.inf.elte.hu/probarch/03/register-en.pdf

'Tunelul groazei infoarena':http://infoarena.ro/problema/tunel

'Tunelul groazei':problema/tunel
'SGU 200':http://acm.sgu.ru/problem.php?contest=0&problem=200
'TC CoinGame':http://www.topcoder.com/stat?c=problem_statement&pm=6005