For more information see Copyright Resources to Support Publishing and Teaching
EXAMPLE: Visscher, Claes Janszoon. Leonis Belgici. Scale not given. "David Rumsey Map Collection." 1611. <http://www.davidrumsey.com/luna/servlet/detail/RUMSEY~8~1~275937~90049132:Leonis-Belgici-?amp;qvq=sort:Pub_List_No_InitialSort,Pub_Date,Pub_List_No,Series_No;lc:RUMSEY~8~1&mi=8&trs=60081&sort=Pub_List_No_InitialSort,Pub_Date,Pub_List_No,Series_No&cic=RUMSEY~8~1&widgetType=detail&nsip=1&nsip=1> (Accessed June 8, 2015).
EXAMPLE: Thera Fresco. Scale not given. In: Harley, J.B. & Woodward, David. The History of Cartography: Cartography in Prehistoric, Ancient, and Medieval Europe and the Mediterranean. Chicago: University of Chicago Press, 1987, Plate 3.
EXAMPLE: Gough Map of Britain. Scale not given. In: Lilley, Keith D., Christopher D. Lloyd, and Bruce M. S. Campbell. "Mapping the Realm: A New Look at the Gough Map of Britain (c.1360)," Imago Mundi: The International Journal for the History of Cartography, 61:1 (2009): 29.
EXAMPLE: Prakash, Om. Kingdom of Shivaji. Scale ca. 1:1,875,000. Delhi: All India Educational Supply Co., 1986.
EXAMPLE: University of Pennsylvania. "University of Pennsylvania campus plan, circa 1796-1802.". Scale not given. ca. 1796-1802. Manuscript collection. Kislak Center for Special Collections, Rare Books and Manuscripts, Philadelphia. Ms. Oversize 45
You may also want to check out North Carolina State University's Guide to Citing Maps
* adapted from Kollen, C., Shawa, W., & Lasgaard, M. (2010). Cartographic citations: A style guide (Second ed.). Chicago: American Library Association.
† includes maps originally found in books/atlases, periodicals, manuscripts, and sheet maps now found on websites