Good reference for string diagrams

Question

I try to learn about string diagrams, like explained here.

First question: Is also some good written introduction to this topic?

Second question: I found The Geometry Of Tensor Calculus, which seems to be the right thing for me, but they are concerned with monodial categories, in contrary to the video which is concerned about natural transformations, it seems to me. Is there some easy way to interpret the content of the paper in terms of natural transformations between functors between (non-monoidal) categories?

Answer 1

• John Baez, Aaron Lauda, Higher-Dimensional Algebra V, arXiv
• Dan Mardsen, Category theory using string diagrams, arXiv
• Peter Selinger, A survey of graphical languages for monoidal categories, arXiv