paper here - one version at least
http://arc.aiaa.org/doi/10.2514/1.B36120
a pilot wave version of quantum mechanics is suggested as the basis for a mechanism.
"If the vacuum is indeed mutable and degradable as was explored, then it might be possible to do/extract work on/from the vacuum, and thereby be possible to push off of the quantum vacuum and preserve the laws of conservation of energy and conservation of momentum. It is proposed that the tapered RF test article pushes off of quantum vacuum fluctuations, and the thruster generates a volumetric body force and moves in one direction while a wake is established in the quantum vacuum that moves in the other direction."
or give this a go
http://www.emdrive.com/theorypaper9-4.pdf