Stirling academic

http://www.unicopter.com/1311.pdf Note academic links and conference papers such as International Stirling conference.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19780016056_1978016056.pdf Nasa

http://stinet.dtic.mil/cgi-bin/GetTRDoc?AD=ADA113409&Location=U2&doc=GetTRDoc.pdf Military