Francisco Jose Brito Castro Carmelo Militello A Modal Error Indicator Based on a Work-Cancellation Property of Energy-Orthogonal Finite Elements. 569-582 2001 2 International Journal of Computational Engineering Science 4 http://www.worldscinet.com/ijces/02/0204/S1465876301000453.html db/journals/ijces/ijces2.html#CastroM01