Northwestern University, Evanston, Ill. Dept. of Geography. (1952). The rural land classification program of Puerto Rico. s.n.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNorthwestern University, Evanston, Ill. Dept. of Geography. The Rural Land Classification Program of Puerto Rico. Evanston, Ill: s.n, 1952.
एमएलए (9वां संस्करण) प्रशस्ति पत्रNorthwestern University, Evanston, Ill. Dept. of Geography. The Rural Land Classification Program of Puerto Rico. s.n, 1952.
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