The following question has a 500 points bounty on MSE that soon comes to an end, and no answer
as expected was given yet. How would a professional solve the problem? Wish you succcess.
http://math.stackexchange.com/questions/1261861/calculate-in-closed-form-int-01-int-01-fracdx-dy1-xy1-x1-yhttps://math.stackexchange.com/questions/1261861/calculate-in-closed-form-int-01-int-01-fracdx-dy1-xy1-x1-y