To understand recursion, one of the most important concepts in programming languages, you could watch the movie, Chris Nolan’s *Inception*: it is about a dream within a dream within a dream, …and, read two statistical papers by Professor Robert Newcombe, one of the most prolific statisticians:

**Two-sided confidence intervals for the single proportion: comparison of seven methods.**

Newcombe RG, Stat Med , Volume 17 , 8 (April 1998) pp.857-**872********Interval estimation for the difference between independent proportions: comparison of eleven methods.**

Newcombe RG, Stat Med , Volume 17 , 8 (April 1998) pp.**873**-890

These two widely cited papers evaluate 7 and 11 methods to calculate single proportion (paper A) and the difference between proportions (paper B), respectively. Further more, they were in the same issue of *Statistics in Medicine*(Volume 17, 1998), and, they were also cross referenced! So here is a live story about recursive referencing(thanks to Prof. Newcombe):

- An author writes two papers, A and B;
- Paper B is in the bibliographic reference session of paper A;
- Paper A is also in the bibliographic reference session of paper B;
- Paper A and paper B are in the same issue of a journal.

Note that for Prof. Newcombe’s two linked papers, it is common and acceptable in publication practices. Recently I used these two wonderful papers to learn CI calculation and this post just want to lead to the concept of “recursion” (reference in reference in reference).