I've been reading some academic papers such as

http://rwbclasses.groups.et.byu.net/lib/exe/fetch.php?media=quadrotor:beardsquadrotornotes.pdf

and 

http://andrew.gibiansky.com/blog/physics/quadcopter-dynamics/

There are only three PIDs in these papers and they seem to control the the attitude by measuring the desired angle and measured angle. 

Is it possible to only use three Stabilization PIDs to control the Quad. for example, in a plus mode quadcopter, the motor output of the front motor would be described as

M1=[mg/4*cos(phi)*COS(Pheta)]+[RolePID/2]+[YawPID/4]