a, b, c, d, 
-a^3*d+b^4
-a^3*c+a*b^3
-a*c^3*d+a*d^4+b*c^4-b*c*d^3
-b*c^3*d^2+b*d^5+c^6-c^3*d^3
a*c^5-a*c^2*d^3-b^2*c^3*d+b^2*d^4
-a^3*d^3+a^2*c^4-a^2*c*d^3+a*b*d^3
-a^3*d^3+a*b*c^3
-a^3*c*d^2+a*b^2*c^3-a*b^2*d^3+b^3*c*d^2
-a^3*c^2*d+a^2*b*c^3-a^2*b*d^3+b^3*c^2*d
-a^3*b*d^2+a^3*c^3
a^4*c^2-a^3*b^2*d
