We calculate analytically the three-loop planar master integrals relevant for
heavy-to-light form factors using the method of differential equations. After
choosing a proper canonical basis, the boundary conditions are easy to be
determined, and the solution of differential equations is greatly simplified.
The results for seventy-one master integrals at general kinematics are all
expressed in terms of harmonic polylogarithms.Comment: 18 pages, 2 figure