They can be stored alongside the normal vector (the 3rd component can be recalculated in the shader) and the height, or put into its own L/A texture, combined with the height. The author suggests ...

Both at gimp-normalmap and gimp-dds, we have an incorrect usage of $(LD) at the Makefile. We have $(LD) being used to link all the objects together. However, this is incorrect, $(CC) should have been ...