Given a sentence and two mentions from the text (arguments), indicate a phrase (a verb or noun phrase) that describes the relationship between the provided arguments.

Sentence: 'The VIAGRA is still tremendous , but VIAGRA is exchanger silly buggers with VIAGRA certain side effects Buy Viagra Online .', Argument/Subject 1: 'viagra', Argument/Subject 2: 'online'
buy

Sentence: 'Greensboro is served by the Piedmont Triad International Airport .', Argument/Subject 1: 'greensboro', Argument/Subject 2: 'piedmont triad international airport'
be serve by

Sentence: 'Newcastle eCityGuide is an online guide to the city of Newcastle , New South Wales .', Argument/Subject 1: 'newcastle', Argument/Subject 2: 'new south wale'

be city in