Scope note: This class comprises identifiers that are not only designed to be unique for the thing they identify, but also to ensure, by following adequate rules based on widely known and accepted properties for their generation, that an independent agency using the same rule would create the same identifier for the same thing. F50 Controlled Access Point covers the notion of both “preferred” and “variant” forms. It does not cover the notion of “cross references”. A cross reference may not uniquely identify one entity, but can be shared by two or more entities, regardless of whether it displays the same structural characteristics as preferred controlled access points. Examples: - ‘Maxwell equations’ [preferred subject access point from LCSH, http://lccn.loc.gov/sh85082387, as of 19 November 2012] - ‘Equations, Maxwell’ [variant subject access point, from the same source] - ‘Gončarova, Natalʹâ Sergeevna (1881-1962)’ [preferred access point for a personal name, from the authority file of the National Library of France, http://catalogue.bnf.fr/ark:/12148/cb119547494/PUBLIC, as of 15 June 2012] - ‘Гончарова, Наталья Сергеевна (1881-1962)’ [parallel access point from the same source] - ‘Goncharova, Natalia (1881-1962)’ [variant access point from the same source] - LC control no.: sh 85082387 LCCN permalink: http://lccn.loc.gov/sh85082387 HEADING: Maxwell equations 000 00455cz a2200181n 450 001 4732904 005 20120327093200.0 008 860211|| anannbabn |b ana 010 __ |a sh 85082387 035 __ |a (DLC)sh 85082387 035 __ |a (DLC)79589 040 __ |a DLC |c DLC 150 __ |a Maxwell equations 450 __ |a Equations, Maxwell 550 __ |w g |a Differential equations, Partial 550 __ |w g |a Electromagnetic theory 906 __ |t 70-- |u ---- |v 0 953 __ |a xx00