Frey, C. (1926). The Independence Square neighborhood: Historical notes on Independence and Washington Squares, lower Chestnut Street, and the insurance district along Walnut Street, in Philadelphia, together with some account of the buildings, events, and personages of State House Row. Philadelphia: The Penn Mutual Life Insurance Co..

Frey, Carroll. The Independence Square Neighborhood: Historical Notes On Independence and Washington Squares, Lower Chestnut Street, and the Insurance District Along Walnut Street, in Philadelphia, Together With Some Account of the Buildings, Events, and Personages of State House Row. Philadelphia: The Penn Mutual Life Insurance Co., 1926.

Frey, Carroll. The Independence Square Neighborhood: Historical Notes On Independence and Washington Squares, Lower Chestnut Street, and the Insurance District Along Walnut Street, in Philadelphia, Together With Some Account of the Buildings, Events, and Personages of State House Row. Philadelphia: The Penn Mutual Life Insurance Co., 1926.