$UserAddOnsDirectory
Since Version 5 (released in 2003), $UserAddOnsDirectory has been superseded by $UserBaseDirectory.
Wolfram Research (1988), $UserAddOnsDirectory, Wolfram Language function, https://reference.wolfram.com/language/ref/$UserAddOnsDirectory.html.
Text
Wolfram Research (1988), $UserAddOnsDirectory, Wolfram Language function, https://reference.wolfram.com/language/ref/$UserAddOnsDirectory.html.
CMS
Wolfram Language. 1988. "$UserAddOnsDirectory." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/$UserAddOnsDirectory.html.
APA
Wolfram Language. (1988). $UserAddOnsDirectory. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$UserAddOnsDirectory.html