Superset 
Superset[x,y,…]
displays as .
Details

- Superset[x,y,…] has no built-in meaning.
is by default interpreted as Superset[x,y].
can be entered as \[Superset] or
sup
.
Examples
Wolfram Research (1996), Superset, Wolfram Language function, https://reference.wolfram.com/language/ref/Superset.html.
Text
Wolfram Research (1996), Superset, Wolfram Language function, https://reference.wolfram.com/language/ref/Superset.html.
CMS
Wolfram Language. 1996. "Superset." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Superset.html.
APA
Wolfram Language. (1996). Superset. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Superset.html