Errata for K.Xu and N.Hale - Explicit construction of rectangular differentiation matrices * The start of the final paragraph in section 5.1 should read: "Additionally, terms of the form $(1 − \tau_{i,n}^2)^{1/2}$ ...". * There is a negative sign missing in the "negative sum trick", equation (5.6) $$[D_{m,n}]_{il} = - \sum_{j=0,j\not=l}^{n-1}[D_{m,n}]_{ij} ...$ We thank Prof. Esmaeili of the University of Kurdistan for notifying us of these errors.