Refine explanations of backdoor criterion and IV #44

Job	Run time
call-workflow / get-branches	6s
call-workflow / build-books (3-awesome-causal-inference-pythonmainatepropensity_score_and_dml)	18s
call-workflow / build-books (10-awesome-causal-inference-pythonmainatesdid)	14s
call-workflow / build-books (15-awesome-causal-inference-pythonmaincate_and_policypolicy_learning)	14s
call-workflow / build-books (43-causal-inference-with-interference)	15s
call-workflow / build-books (32-53-case-study-코드-변환)	18s
call-workflow / build-books (14-awesome-causal-inference-pythonmainateiv)	17s
call-workflow / build-books (33-비모수적-cate-추정-방법론-구현)	17s
call-workflow / build-books (31-policy-learning-53-case-study)	12s
call-workflow / build-books (9-awesome-causal-inference-pythonmainatesc)	12s
call-workflow / build-books (main)	47s
call-workflow / build-books (revert-26-feat/ps-ipw-dr-notebook)	12s
call-workflow / deploy-books	1m 41s
call-workflow / summarize	6s
	5m 9s

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