(1969). Pennsylvania statistical abstract: Eleventh annual edition January 1969. Harisburg: Bureau of Statistics.
Παραπομπή Chicago StylePennsylvania Statistical Abstract: Eleventh Annual Edition January 1969. Harisburg: Bureau of Statistics, 1969.
Παραπομπή MLAPennsylvania Statistical Abstract: Eleventh Annual Edition January 1969. Harisburg: Bureau of Statistics, 1969.
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