"The Bluebook is generally accepted as the paragon of citation style for law schools and the legal industry." Christine Hurt, The Bluebook at Eighteen: Reflecting and Ratifying Current Trends in Legal Scholarship, 82 Ind. L.J. 49, 51 (2007).
For information about The Bluebook and it's uses, check out Georgetown Law Library's Bluebook Guide.
The Bluebook: A Uniform System of Citation Harvard Law Review Association
Library has 21st (2020), 20th (2015), 19th (2010), 18th (2005), 17th (2000), 15th (1991), 14th (1986), 13th (1981), and 12th (1976) editions.