Here you can find some links that I’ve found very important in my work in diagrams. If you are interested in diagrams then you can check my research on Diagram-Based Computer Based Assessment and my diagrammatics course!
In 2001 I’ve compiled the resources for a four-part “Diagrammatics” course. I’ve taught it few times. Sometimes as a full-blown four hours lecture but most times I just pick up the relevant bits.