1. Anayoha, R. (2017). The History of Artificial Intelligence. http://sitn.hms.harvard.edu/flash/2017/history-artificial-intelligence/.
2. Bera, A. (2019). Is Siri better than Google? – 16 interesting Siri statistics. https://safeatlast.co/blog/siri-statistics/#gref.
3. Apple was a little behind on Siri privacy, now it’s way ahead;Bohn;The Verge.,2019
4. Siri, Alexa, and other digital assistants: A study of customer satisfaction with AI applications;Brill;Journal of Marketing Management,2019
5. Bronstein, M. (2019), “Bringing You the Next Generation Google Assistant,” https://blog.google/products/assistant/next-generation-google-assistant-io/.