Gradient methods can offer unique solutions to separation problems, but transferring a gradient method from the literature, between laboratories, or even within the same laboratory can be a challenging process.
John W. Dolan
p. 458, righthand column, 2nd full paragraph, second sentence cites reference (4). This should be reference (3). The oversimplified gradient was described in LCGC 32(4) (2013) in the last paragraph before the summary on p. 305.
p. 460, Figure 3. Note that the curly brackets under the figure are scaled wrong their junction should be shifted left to align directly under the vertical line labeled t(subscript)D. Also, the righthand curly bracket is mislabeled it should be “1/2 t(subscript)G” not “1/2 t(subscript)D”