Citation Hunt

The Wikipedia snippet below is not backed by a reliable source. Can you find one?

Click I got this! to go to Wikipedia and fix the snippet, or Next! to see another one. Good luck!

In page Fuzzy set:

"

where α > 0 {\displaystyle \alpha >0} is a steepness parameter and exp ( x ) = e x {\displaystyle \exp(x)=e^{x}} .[citation needed]