Concordances and Lexicons are cited as you would a reference source such as a dictionary or encyclopedia.
Footnote:
¹ W. S. Lasor, "Sennacherib," in The International Standard Bible Encyclopedia (Grand Rapids, MI: William B. Eerdmans Publishing Company, 1988), 395.
Bibliography:
Lasor, W. S. "Sennacherib." In The International Standard Bible Encyclopedia. Grand Rapids, MI: William B. Eerdmans Publishing Company, 1988.