On August 19, 1940, F. W. Reichelderfer, Chief of the Bureau, signed an Administrative Circular declaring that all communications given a wide distribution would be designated "Circular Letters" in order to clear the confusion over its definition from previous years. Such letters may contain announcements of certain events or general information to Bureau personnel that may be of a temporary nature. Circular Letters are numbered serially followed by a dash and the last two numerals of the calendar year of issue. Circular Letters were signed by the Chief or Acting Chief of the Bureau and were dispersed to all first-order stations.