You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "who did the original heard it through the grapevine?" whose answer is Gladys Knight & the Pips.
Each document should contain about 30 words, and these documents should contain useful information.

Query: original artist of Heard It Through the Grapevine
Useful Output:

Doc 1: Marvin Gaye - I Heard It Through The Grapevine (Lyric Video) · Comments867.
Doc 2: Norman Whitfield and Barrett Strong wrote the tune in 1966. Marvin Gaye was not the first Motown artist to record it. Smokey Robinson and
Doc 3: Gladys Knight & The Pips - I Heard It Through The Grapevine (Lyric Video) · Comments.
Doc 4: Written by Jim “Bruiser” Krueger and performed with Dave Mason. Billy Dean covered it on his 1993 Fire in the Dark album and had more commercial
Doc 5: Originally written by Motown's Barrett Strong and Norman Whitfield, the song riffed on the concept of the “human grapevine” that slaves coined