On a Boeing 737, can the APU, BY ITSELF, provide enough thrust to move the plane while on the ground?
I can't reference to a document, but I can say with reasonable certainty that the answer is no, because like any turboprop or turboshaft, the APU has nearly all of the energy of its mass flow extracted for bleed air, or for torque production purposes for electricity, so that there is little thrust energy available.  Turboprops typically get maybe 10% of the total energy available from the engine as exhaust thrust.
So using that number for an APU in an airplane the size of a 737 that is making, say, 650 shaft horsepower (just an educated guess; the actual number is surprisingly hard to find), it's producing a thrust equivalent to roughly 65 hp statically out its tailpipe, which equates to perhaps 2-300 lbs of static thrust (I recall that it's something like 4lbs thrust = 1 HP in the static case) at most.  That would be if the tailpipe was even optimized for making thrust in the first place (tapered to accelerate the flow), which they are generally not.
So, figure on a few hundred pounds of push at most, probably quite a bit less, which isn't going to move a 737 unless it's on some kind of near-frictionless surface, or in outer space.