The Bluebook 20th ed. by Harvard Law School was published in the summer of 2015. While Harvard does not provide an official reference guide / cheat sheet / summary of the Bluebook (unlike the OSCOLA Cheat Sheet), here are our top two unofficial cheat sheets available on the internet:
20th Edition Bluebook PDF (Full Text)
1. By Penn State Law (The Pennsylvania State University)
2. By STU Writing Centre
In case of any doubt, mooters are advised to refer the original Bluebook 20th ed. for correct referencing.