Richard Cole Zvi Galil Ramesh Hariharan S. Muthukrishnan Kunsoo Park Parallel two dimensional witness computation. 20-67 2004 188 Inf. Comput. 1 http://dx.doi.org/10.1016/S0890-5401(03)00162-7 db/journals/iandc/iandc188.html#ColeGHMP04