- https://github.com/RubyMoney/money
- http://css.dzone.com/books/practical-php-patterns/basic/practical-php-patterns-value
- http://www.codeproject.com/KB/recipes/MoneyTypeForCLR.aspx
- http://stackoverflow.com/questions/1679292/proof-that-fowlers-money-allocation-algorithm-is-correct
- http://timeandmoney.sourceforge.net/
- http://www.joda.org/joda-money/
- http://en.wikipedia.org/wiki/Currency_pair
- https://github.com/RubyMoney/eu_central_bank
- http://en.wikipedia.org/wiki/ISO_4217