Calendar month means the period of time between a designated day of any given month and the date preceding a similarly designated day of the following month.

Citizen of the United States means a person who under applicable law acquired citizenship of the United States by birth, by naturalization, or by derivation.

Dependent husband means the surviving male spouse of a deceased civilian American citizen who was married to the deceased at the time of her death by a marriage valid under the applicable law of the place where entered into.

Force hostile to the United States means any organization or force in Southeast Asia, or any agent or employee thereof, engaged in any military or civil activities designed to further the prosecution of its armed conflict against the Armed Forces of the United States during the Vietnam conflict.

Southeast Asia means, but is not necessarily restricted to, the areas of Vietnam, Laos, and Cambodia.

Went into hiding means the action taken by a civilian American citizen when that person initiated a course of conduct consistent with an intention to evade capture or detention by a hostile force in Southeast Asia.