In North America, the Master of Theology (Th.M. or M.Th.) is considered by the Association of Theological Schools to be the minimum educational credential for teaching theological subjects in accredited schools. The degree is usually earned after the Master of Divinity (M.Div.) or an equivalent of three years of graduate studies in theology. This degree can range from a one or two years of specialized advanced studies in theological research. It may or may not require comprehensive subject exams and a research thesis. The M.Th. is usually designed as an advanced academic degree with an emphasis on academic research. It is usually a second theological degree after a M.A. or a Master of Divinity (M.Div).