Which are the sources of siri?

Which are the sources of siri?

According to ProgrammableWeb, Apple Siri uses more than 35 APIs [1].  For instance, Siri accounts for about a quarter of the queries fielded by Wolfram|Alpha [2].  Yelp is another of the APIs Siri uses [3].

[1] http://blog.programmableweb.com/2011/10/04/are-there-open-apis-behind-apples-new-voice-commands/

[2] http://www.nytimes.com/2012/02/07/technology/wolfram-a-search-engine-finds-answers-within-itself.html

[3] http://officialblog.yelp.com/2012/03/your-iphone-personal-assistant-now-with-more-yelp.html

See also:

Which topics on Quora are related to the technology behind Apple Siri?

What software stack does Siri use?