APA (7th ed.) Citation

Easton, S. C., & Wieruszowski, H. (1961). The era of Charlemagne. Van Nostrand.

Chicago Style (17th ed.) Citation

Easton, Stewart C., and Helene Wieruszowski. The Era of Charlemagne. Princeton, N.J.: Van Nostrand, 1961.

MLA (9th ed.) Citation

Easton, Stewart C., and Helene Wieruszowski. The Era of Charlemagne. Van Nostrand, 1961.