Annette,
Believe Microsoft Corporation is considered both author and publisher of
the software. Corporate offices are located in Redmond, Washington.
I'd cite as below:
Microsoft Corporation. (1996). Microsoft Office 97 Standard
Edition: PowerPoint [Computer
Software]. Redmond,
WA: Microsoft Corporation.
(APA Manual ref #3, Bottom of page 221).
In text:
Participants were presented the ambiguous stimuli at intervals of
_______ using Microsoft PowerPoint presentation software (Microsoft
Corporation, 1996).
Best,
CJC
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