In cases where a concern deals with a number of subdivisions, the auditor will find it convenient to use the subdivision history described in Section35 (Form 31), entering thereon all the particulars as to the cost price, area, name of vendor, size of lots, method of payment, terms of contract, etc.; and, at the close of his audit, entering thereon the number of lots unsold and the book value thereof. These sheets, when bound and kept from year to year, form a convenient means of preserving information which is needed each time an audit is made. The data should be obtained from the original papers and not from any hearsay evidence, as such contracts, especially of the nature of selling contracts, involve a great many details which may not be transcribed accurately from memory.