citing maxima



What is the appropriate way to cite maxima in an academic context?
Is

The Maxima Group. Maxima, a Computer Algebra System. Version 5.18.1
(2009). http://maxima.sourceforge.net/

satisfactory? This mimics GAP's stated preference.

On the other hand, maxima at start-up and in its documentation makes
special reference to Schelter.

I have looked at a number of documents and have not found a satisfactory
answer.

Leo

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