Não informado. (1968). Research Results Digest. National Cooperative Highway Research Program.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Research Results Digest. Washington: National Cooperative Highway Research Program, 1968.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Research Results Digest. National Cooperative Highway Research Program, 1968.
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