I maintain a set of open calculus texts for our calculus sequence, which has four courses (Calculus I-IV). Each course has its own corresponding open text. Occasionally the text for a later course will need to refer back to a result in one of the earlier texts.
As usual, I accomplish this using the xr package, loading the previous texts as external documents, and everything works fine, except for the following issue:
Because an instructor for a prerequisite course in the sequence might not get through all the material they need to, I repeat some sections. For example the first chapter in Calculus III might contain several sections from the last chapter of Calculus II.
This results in a proliferation of multiply-defined references from the repeated sections when using xr to cross-reference the earlier texts.
Is there any way to configure the xr package to ignore references from the repeated sections?
Example: overall project has BookA.tex and BookB.tex in the top level of the directory tree. There are subdirectories such as /text (containing the .tex files for each section), /figures, etc.
BookA has two sections, included using
BookB is a continuation of BookA, but due to overlap between courses that use BookA and BookB, it also includes Section2. So BookB has
in the preamble, and in the document, has
Since Section2 appears in both BookA and BookB, using BookA for cross referencing creates multiply-defined references.
I want a way to reference BookA (because Section3 has references to Section1, say) but omit the sections that also occur in BookB.