A 1980 Maryland law specifies, "(a) On even numbered calendar dates gasoline shall only be purchased by operators of vehicles bearing personalized registration plates containing no numbers and registration plates with the last digit ending in an even number. This shall not include ham radio operator plates. Zero is an even number; (b) On odd numbered calendar dates ..." Partial quotation taken from Department of Legislative Reference (1974), Laws of the State of Maryland, Volume 2, σελ. 3236, http://books.google.com/books?q=%22ham+radio+operator+plates.+Zero+is+an+even+number%22, ανακτήθηκε στις 2 June 2013
