If the patent has multiple dates listed use the issue date as publication date.
It may be difficult to find a persistent URL or DOI to include in your citation
Standard format for citation
[#] A. Author, "Title of patent," Patent Number, Month Day, Year. Available: URL or Database Name, Accessed on: Month Day, Year. Available: Source.
Canadian patent application
 P. Di Benedetto and G. Colacitti. "Unmanned Aerial Vehicle Delivery System," CA 3031287, Jan 18, 2019, http://www.ic.gc.ca/opic-cipo/cpd/eng/patent/3031287/summary.html?query=Drone+delivery&type=basic_search, Accessed on Jul 25, 2019. [Online].
 F. Buevich et al. "Temporarily Stiffened Mesh Protheses," CA 2637578, Mar 31, 2015, http://www.ic.gc.ca/opic-cipo/cpd/eng/patent/2637578/summary.html?query=prosthesis+medical&type=basic_search, Accessed on Jul 25, 2019. [Online].