Quote:

Matt Finley
And I concur that a 13th implies not only that the dominant 7th is present, but also the 9th and often the 11th.






I respectfully disagree.
Since I only have five fingers on my hand, I consider a 13th chord to be a triad or dominant chord with only the 13th added.
Though an extended version 13th could have the 9th or 11th added.
And Wikipedia agrees with me:



A thirteenth chord is the stacking of six thirds, the last being above the 11th of an eleventh chord[1]. Thus a thirteenth chord is a tertian (built from thirds) chord containing the interval of a thirteenth, and is an extended chord if it includes the ninth and/or the eleventh. "The jazzy thirteenth is a very versatile chord and is used in many genres."[2] Since 13th chords tend to become unclear or confused with other chords when inverted they are generally found in root position.

http://en.wikipedia.org/wiki/Thirteenth