  In the survey paper, along one of main lines of bounding the ratio of two
gamma functions, we look back and analyse some known results, including
Wendel's, Gurland's, Kazarinoff's, Gautschi's, Watson's, Chu's,
Lazarevi\'c-Lupa\c{s}'s, Kershaw's and Elezovi\'c-Giordano-Pe\v{c}ari\'c's
inequalities, claim, monotonic and convex properties. On the other hand, we
introduce some related advances on the topic of bounding the ratio of two gamma
functions in recent years.
