Given the events described below in triple quotes, for each event extract the person mentioned and the corresponding date.
Each person/date pair should be listed on a separate line in the form: (date, person)
If no person is mentioned, simply list "unknown" next to the date.

 

"""1956 - NAME_1 coined the term ‘artificial intelligence’ and had the first AI conference.
1987 - NAME_2 published The Society of Mind, a theoretical description of the mind as a collection of cooperating agents.
1997 - The Deep Blue chess machine (IBM) defeats the (then) world chess champion, NAME_3.
2002 - The first commercially successful robotic vacuum cleaner was created.
2016 - Google DeepMind's AlphaGo defeated NAME_4, a 9 dan professional Korean Go champion."""