Detective Comics
Detective Comics is an American comic book series published by DC Comics. The first volume, published from 1937 to 2011 (and later continued in 2016), is best known for introducing the superhero Batman in "Detective Comics" #27 (cover dated May 1939).
World's Finest Comics
The idea for "World's Best" #1 originated from the identically formatted 1940 "New York World's Fair Comics" featuring Superman, Batman, and Robin with 96 pages and a cardboard cover. The year before there was a similar 1939 "New York World's Fair Comics" featuring Superman but without Batman and Robin because Bill Finger and Bob Kane had not yet created them.