The original amscd package provides a CD environment that emulates the commutative diagram capabilities of AMS-TEX version 2.x. This means that only simple rectangular diagrams are supported, with no diagonal arrows or more exotic features.
 
This enhancement package amscdx implements double (”fat”) and dashed arrows also in both directions  (left-right and up-down), and color attributes for arrows and their annotations. The restriction to rectangular geometry remains. This nevertheless allows the drawing of a much broader class of "commutative-diagram-like" diagrams.

License: The LaTeX Project Public License 1.3c. (c) Martin Vermeer.