In 1979, J.J. Kohn proposed an algorithm to produce subelliptic multipliers for the dbar-Neumann problem. But Kohn's original procedure gives no effective bound on the order of subellipticity in subelliptic estimates. In 2010, Y.-T. Siu obtained a new effective procedure to terminate Kohn's algorithm for so-called special domains. In this talk, we explain Siu's effective algorithm for multipliers as well as Kohn's full radical algorithm and their difference. Then we present a triangular system of multipliers for special domains. Finally, we give applications of triangular system to more general domains. This is a joint work with D. Zaitsev.