http://books.google.com/books?id=uysYAAAAYAAJ&pg=RA1-PA23&img=1&zoom=3&hl=en&sig=ACfU3U2nWYO6QMY_YTUFNvbJdhDoWhSSGg&ci=26%2C343%2C438%2C1365&edge=0
十三行行欠问题，详细。