Churella. The Pennsylvania Railroad, Volume 1. University of Pennsylvania Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रChurella. The Pennsylvania Railroad, Volume 1. University of Pennsylvania Press.
एमएलए (9वां संस्करण) प्रशस्ति पत्रChurella. The Pennsylvania Railroad, Volume 1. University of Pennsylvania Press.
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