Books, articles and websites that may be of interest.
Interaction Design for Complex Problem Solving
Barbara Mirel's book on complex problem solving is the volume that kicked off this adventure for me. I wholeheartedly advocate buying the book as it’s pretty exhaustive and very research focussed, though having said that, I would add a gentle warning that it's not exactly a page turner — though why should it need to be — just keep a coffee close while reading.
An oldie but a goodie, Jeff Johnson and Austin Henderson (Conceptual Model OGs) give a talk about what Conecptual Models are along with how and why to use them.
Morgane Peng is one of the very few practitioners of Complex UX talking and writing about this work. She's done a few talks on the subject which are well worth your time, you'll find the links on her site.