Mignola, M. (2019). Hellboy: 25 years of covers: 25 years of covers. Dark Horse Comics, LLC..
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रMignola, Mike. Hellboy: 25 Years of Covers: 25 Years of Covers. Cleveland: Dark Horse Comics, LLC., 2019.
एमएलए (8वां संस्करण) प्रशस्ति पत्रMignola, Mike. Hellboy: 25 Years of Covers: 25 Years of Covers. Dark Horse Comics, LLC., 2019.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.