How do you track dependencies for your co-authors?
I and one or more co-authors, sometimes geographically distributed, are working on a set of related documents. Sometimes I will make a change in my part that affects someone else's part; this could be anything from changing a name to adding a new concept (that later parts should then use or reference) to changing the scenario for a running example. For large changes one hopes we'd all be talking about it first, but sometimes smaller changes come up that it's not worth calling a meeting about. How do you track those dependencies so you don't lose track of them?
Things we have tried include:
Send email. Easy but can get lost.
Have a central place to leave notes (shared document, wiki page, etc). This works pretty well if you can sort it by who/what is affected, so each person has just one place to look, but it can be kind of unwieldy if dependencies are vague or numerous.
Use a bug-tracking system: works if everybody is using the same tools and the folks overseeing the bug database don't mind, but that's not always the case.
What are better ways to manage inter-connected work with co-authors?
Clarification: I'm talking about cases where I make a change and others will then have to make updates to their work, not about cases where I make all the relevant changes myself.