APA (7 वां संस्करण) प्रशस्ति पत्र

Warren Penn, R. Foreword to Brother to Dragons: A Play in Two Acts / Robert Warren Penn. Robert Penn Warren's "Brother to Dragons" : a discussion.(1983).

शिकागो शैली (17वां संस्करण) प्रशस्ति पत्र

Warren Penn, Robert. "Foreword to Brother to Dragons: A Play in Two Acts / Robert Warren Penn." Robert Penn Warren's "Brother to Dragons" : A Discussion.(1983) .

एमएलए (8वां संस्करण) प्रशस्ति पत्र

Warren Penn, Robert. "Foreword to Brother to Dragons: A Play in Two Acts / Robert Warren Penn." Robert Penn Warren's "Brother to Dragons" : A Discussion.(1983), .