After the application for patent is made, details about the patent application are published in Patent office Journal of respective country. Publication Number is generally the entry no. in that journal, and is usually in the form of, e.g., US20150150184; “US” referring to the Country Code (in this case – United States) and “20150150184” is the serial no. of the publication. It may be noticed that the first four digits of the publication number provides the year of publication, in this case 2015.