Title from PDF caption (viewed Jan. 15, 2009)., "7/24/79.", and AC 91-13B, dated January 17, 1978, is cancelled.
Electronic reproduction. [Washington, D.C.] : Dept. of Transportation, Federal Aviation Administration,  Mode of access: World Wide Web. System requirements: PDF reader.
Mode of access: Internet at the FAA web site. Address as of 1/15/09: http://www.airweb.faa.gov/Regulatory%5Fand%5FGuidance%5FLibrary/rgAdvisoryCircular.nsf/0/0a6bf63c8fb95285862569d900744829/$FILE/ac91-13c.pdf; current access available via PURL.