Resumen
We study the problem of computing a preemptive schedule of equal-length jobs with given release times, deadlines and weights. Our goal is to maximize the weighted throughput. In Graham's notation this problem is described as (1|rj;pj=p;pmtn|? wjUj). We provide an O(n4)-time algorithm, improving the previous bound of O(n10).

Resumen
We consider the problem of scheduling n preemptive jobs on a single machine to minimize total tardiness, subject to agreeable due dates, i.e., a later release date corresponds to a later due date. We prove that the problem is -hard in the ordinary sense by showing that it is -hard, and deriving a pseudo-polynomial algorithm for it.