Etymology
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op. cit. 

abbreviation of Latin opus citatum "the work quoted;" see opus; citatum is neuter singular past participial of citare "to call, call forward, summon" (see cite).

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beat up (v.)
"thrash, strike repeatedly," c. 1900 (v.), from beat (v.) + up (adv.). Earlier it meant "summon (recruits, etc.) by the beating of a drum" (1690s). Beat-up as an adjectival phrase meaning "worn-out" dates to 1946.
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