natbib 매뉴얼 6~7쪽에 보면 \citet*와 \citep* 처럼 별표 붙은 명령을 쓰라고 합니다.

There also exist the starred versions \citet* and \citep* that print the full author list, and not just the abbreviated one. All of these may take one or two optional arguments to add some text before and after the citation.

The starred versions can only list the full authors if the .bst file supports this feature; otherwise, the abbreviated list is printed.

단 newapa 스타일을 쓰는 게 좋겠어요. 

- \bibliographystyle{apalike}

+ \bibliographystyle{newapa}