File:Vchelicopterfight2.jpg

Summary
VC/NVA methods for fighting US helicopters. At the battle of Dak To, on Hill 875, automatic weapons in treetops accounted for several US choppers. Terrence Maitland, A CONTAGION OF WAR: THE VIETNAM EXPERIENCE SERIES, (Boston Publishing Company), 1983, p. 180

Detail: Basically a bunch of Public domain clipart from the US Army and Powerpoint arrows, squares etc. to make the image. Clipart is from US Army website- Fort Sill. All are public domain http://sill-www.army.mil/Graphics/clipart_library.htm

Since Powerpoint is used for the diagram, the following blurb takes care of Microsoft:

"Contains clipart from Microsoft Powerpoint- not for commercial use or resale, per Microsoft guidelines at http://office.microsoft.com/en-us/powerpoint/HP030900871033.aspx, Copyright, Microsoft Corporation. Include this notice with any reuse."