Kolby, J. &. o. (2015). GMAT: DATA Sufficiency Prep Course. Prakash Pub.
Lua i Stíl Chicago (17ú heag.)Kolby, Jeff & others. GMAT: DATA Sufficiency Prep Course. New Delhi: Prakash Pub, 2015.
Lua MLA (9ú heag.)Kolby, Jeff & others. GMAT: DATA Sufficiency Prep Course. Prakash Pub, 2015.
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