A benchmark crude or marker crude is a crude oil that serves as a reference price for buyers and sellers of crude oil. There are three primary benchmarks, West Texas Intermediate (WTI), Brent Blend, and Dubai Crude. Other well-known blends include the OPEC Reference Basket used by OPEC, Tapis Crude which is traded in Singapore, Bonny Light used in Nigeria, Urals oil used in Russia and Mexico's Isthmus. Energy Intelligence Group publishes a handbook which identified 195 major crude streams or blends in its 2011 edition.