ASSIST is a web site used by standardization management to develop, coordinate, distribute, and manage defense and federal specifications and standards, military handbooks, commercial item descriptions, data item descriptions, and related technical documents prepared in accordance with the policies and procedures of the Defense Standardization Program (DSP).
Besides DoD-prepared documents, ASSIST also has selected international standardization agreements, such as NATO standards ratified by the United States and International Test Operating Procedures.
Since it always has the most current information, ASSIST is the official source for specifications and standards used by the Department of Defense.
Find all archived copies of MIL-STD-461, here.