A Guide to the Project Management Body of Knowledge: PMBOK(R) Guide, Project Management Institute, 4th Edition, (2008) - Free Books

http://www.cs.bilkent.edu.tr/~cagatay/cs413/PMBOK.pdf

http://www.works.gov.bh/English/ourstrategy/Project%20Management/Documents/Other%20PM%20Resources/PMBOKGuideFourthEdition_protected.pdf