Transforming an error-tolerant separable matrix to an error-tolerant disjunct matrix

Recently, Chen and Hwang [H.B. Chen, F.K. Hwang, Exploring the missing link among dd-separable, d¯-separable and dd-disjunct matrices, Discrete Applied Mathematics 133 (2007) 662–664] provided a method for transforming a separable matrix to a disjunct matrix. In [D.Z. Du, F.K. Hwang, Pooling Designs and Nonadaptive Group Testing — Important Tools for DNA Sequencing, World Scientific, 2006], Du and Hwang attempted to extend this result to its error-tolerant version; unfortunately, they gave an incorrect extension. This note gives a solution to this problem.