Variable%20Ratio%20Schedule%20(VR)
Here's your citation in American Psychological Association (APA) format:
Variable%20Ratio%20Schedule%20(VR). (n.d.). In Alleydog.com's online glossary. Retrieved from: https://www.alleydog.com/glossary/definition-cit.php?term=Variable%2520Ratio%2520Schedule%2520%28VR%29