Aside from similarities to socialism, early forms of proto-capitalism and free markets were present in the Caliphate, since an early market economy and early form of merchant capitalism developed between the 8th and 12th centuries, which some refer to as "Islamic capitalism". A vigorous monetary economy developed based on the circulation of a stable high-value currency (the dinar) and the integration of previously independent monetary areas. Business techniques and forms of business organisation employed during this time included early contracts, bills of exchange, long-distance international trade, early forms of partnership ("mufawada") such as limited partnerships ("mudaraba") and early forms of credit, debt, profit, loss, capital ("al-mal"), capital accumulation ("nama al-mal"), circulating capital, capital expenditure, revenue, cheques, promissory notes, trusts ("waqf"), startup companies, savings accounts, transactional accounts, pawning, loaning, exchange rates, bankers, money changers, ledgers, deposits, assignments, the double-entry bookkeeping system, and lawsuits. Organisational enterprises similar to corporations independent from the state also existed in the medieval Islamic world. Many of these concepts were adopted and further advanced in medieval Europe from the 13th century onwards.