The AACE International Professional Practice Guides (PPGs) are references containing the most worthwhile existing contributions to the cost engineering field and the advancement of total cost management. Intended to be comprehensive, well organized, and timely, each PPG title is a collection of selected articles from Cost Engineering journal, AACE International Transactions, and other sources to which AACE has rights, covering a particular technical topic area, or industry segment. The PPGs provide an excellent source of reference material and is a welcome addition to any reference library.