Where is cash system of accounting defined??

Amongst the two methods of accounting generally followed in India, i.e. mercantile system and cash system, mercantile system has been defined exhaustively. But what about "cash system of accounting"?? Generally understood meaning of cash system would be that, a cash system of accounting is one where revenue and expense are recorded only when received or paid. But is there any authoritative statement on this?? That is , institute's publication, case law?? Please cite a reference. Thanks in advance.