The Lifting Theorem for Multitensors
  We continue to develop the theory of monads and multitensors. The central result of this paper - the lifting theorem for multitensors - enables us to see the Gray tensor product of 2-categories and the Crans tensor product of Gray categories as part of our emerging framework. Moreover we explain how our lifting theorem gives an alternative description of Day convolution in the unenriched context. 
Michael Batanin, Denis-Charles Cisinski, and Mark Weber
math.CT