Underwater Swimming -- See Skin diving Here are entered works on free diving with the use of mask, fins, and snorkel. Works on free diving with the use of an aqualung are entered under Scuba diving.
Undocumented Aliens -- See Noncitizens Here are entered works on persons who are not citizens of the country in which they reside. When this heading is assigned to works on noncitizens who permanently or temporarily relocate across national borders without complying with the legal requirements of the destination country, the heading Illegal immigration is also assigned.Works on those persons who have no citizenship are entered under Stateless persons.
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Undocumented Immigrants -- See Noncitizens Here are entered works on persons who are not citizens of the country in which they reside. When this heading is assigned to works on noncitizens who permanently or temporarily relocate across national borders without complying with the legal requirements of the destination country, the heading Illegal immigration is also assigned.Works on those persons who have no citizenship are entered under Stateless persons.
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Undocumented Immigration -- See Illegal immigration Here are entered works on the act of permanently or temporarily relocating across national borders without complying with the legal requirements of the destination country. When this heading is assigned to works on persons who immigrate illegally, the heading Noncitizens is also assigned.
