The third Monday in January is reserved to honor the Rev. Dr. Martin Luther King, Jr. It is the only federal holiday formally recognized as a national day of service, “a day on, not a day off.” In the spirit of listening and thinking first, people are warmly encouraged to study the works of King, and to devote time to serious reflection on how we will endeavor toward a healthier, more just world for all. Here are some ways you can learn about and advance his legacy.