$TopDirectory

Since Version 5.0 (released in 2003), $TopDirectory has been superseded by $InstallationDirectory and $BaseDirectory.
Wolfram Research (1996), $TopDirectory, Wolfram Language function, https://reference.wolfram.com/language/ref/$TopDirectory.html (updated 2002).

Text

Wolfram Research (1996), $TopDirectory, Wolfram Language function, https://reference.wolfram.com/language/ref/$TopDirectory.html (updated 2002).

BibTeX

@misc{reference.wolfram_2021_$topdirectory, author="Wolfram Research", title="{$TopDirectory}", year="2002", howpublished="\url{https://reference.wolfram.com/language/ref/$TopDirectory.html}", note=[Accessed: 26-September-2021 ]}

BibLaTeX

@online{reference.wolfram_2021_$topdirectory, organization={Wolfram Research}, title={$TopDirectory}, year={2002}, url={https://reference.wolfram.com/language/ref/$TopDirectory.html}, note=[Accessed: 26-September-2021 ]}

CMS

Wolfram Language. 1996. "$TopDirectory." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2002. https://reference.wolfram.com/language/ref/$TopDirectory.html.

APA

Wolfram Language. (1996). $TopDirectory. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/$TopDirectory.html