resource person
US /ˈriːsɔːrs ˌpɜːrsn/
UK /ˈriːsɔːrs ˌpɜːrsn/

1.
a person who is a source of special knowledge or expertise
:
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The workshop invited a renowned scientist as a resource person to speak on climate change.
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For any questions regarding the new software, please contact our resource person, Sarah.