@xiaohuamao, to be honest I'm not an expert in the pure maths background. The introduction was written by my PhD supervisor, I used the technique in my thesis and then used it again last year.
Take a look at http://www.macs.hw.ac.uk/~simonm/talks/strath.pdf, and the paper https://gdz.sub.uni-goettingen.de/id/PPN243919689_0410?tify=%7B%22view%22:%22info%22,%22pages%22:%5B171%5D%7D
Take a look at http://www.macs.hw.ac.uk/~simonm/talks/strath.pdf, and the paper https://gdz.sub.uni-goettingen.de/id/PPN243919689_0410?tify=%7B%22view%22:%22info%22,%22pages%22:%5B171%5D%7D