Errata
Understanding and Implementing the Finite Element Method
Mark S. Gockenbach
(SIAM 2006)

Note: Positive line numbers start at the top of the page, negative line numbers start at the bottom.

1. Page 90, Line -1: The integral on the right-hand side is missing a factor of $\vert\det(J(u))\vert$. The equation should read
   
   $$\int_Q\kappa (z)\nabla \phi_i(z)\cdot\nabla \phi_j(z)\,dz= \... ...t(J(u)^{-T}\nabla \gamma _j(u)\right)\vert\det(J(u))\vert\,du.$$
   
   

2. Page 167, Algorithm 7.1:
   • Line 10: T.Edges(eptr(2,2)) should be T.Edges(eptr(2),2)
   • Line 12: T.Edges(eptr(2,1)) should be T.Edges(eptr(2),1)
3. Page 172, Algorithm 7.5:
   • Line 10: nonzero should be negative
4. Page 225, Chapter 10: This chapter fails to give any suggestions for further reading about direct methods for sparse systems. An up-to-date treatment that just appeared is Direct Methods for Sparse Linear Systems by Timothy A. Davis (SIAM, 2006).
5. Page 334, Section 15.2: The explicit residual indicator described in this section is due to Ainsworth and Oden (see Section 2.2 of A Posteriori Error Estimation in Finite Element Analysis by Mark Ainsworth and J. Tinsley Oden, reference [2] in the bibliography). The citation was inadvertently omitted.
6. Page 338, Line -4: ``three-point element residual estimator'' should be ``explicit residual estimator.''