1.  Gary Boyd Roberts.  1995.  Ancestors of American Presidents.  New England Historic Genealogical Society, Boston, p. 52.

2.  Rossiter Johnson, ed.  1904.  Twentieth Century Biographical Dictionary of Notable Americans.  Biographical Society, Boston.  In Vol. X, on p. 424:

WILLIAMS, William, signer, was born in Lebanon, Conn., April 18, 1731; son of the Rev. Solomon Williams (1700-76) of Lebanon. He was graduated from Harvard, A.B., 1751, A.M., 1754; studied theology under his father, 1751-52, and in 1755 joined the regiment of Massachusetts volunteers under Col. Ephraim Williams (q.v.) in the invasion of Canada. He was married to Mary, daughter of Gov. Jonathan Trumbull. He was town clerk of Lebanon, Conn., 1756-1801; a representative in the assembly for over fifty years;  colonel of the 12th regiment of militia, 1773-76, and a delegate to the Continental congress, being one of the signers of the Declaration of Independence of July 4, 1776. He was a member of the committee of safety; and expended most of his valuable property on the patriot cause. He was an assistant or councillor, 1780-1804; judge of the county court of Wyndham and probate judge for forty years, and a member of the convention that ratified the constitution of the United States in 1787. The honorary degree of A.M. was conferred on him by Yale in 1753. He died in Lebanon, Conn., Aug. 2, 1811.

3.  Thomas Herringshaw.  1902.  Herringshaw's Encyclopedia of American Biography of the Nineteenth Century.  American Publ. Assn., Chicago.  On p. 1016:

WILLIAMS, WILLIAM, signer of the declaration of independence, was born April 18, 1731, in Lebanon, Conn. He was a member of the assembly of Connecticut; and a justice of  the peace, and was for nearly one hundred sessions, member, clerk or speaker of the house of representatives. At the commencement of the war of the revolution he was a member of the council of safety, and was one of the signers of the declaration of independence. He was a delegate to the continental congress from 1776 to 1778, and again in 1783 and 1784. When the government treasury was drained, he gave to his country what he called his last mite, which amounted to more than two thousand dollars, and was very fortunate in obtaining donations from others. He died Aug. 2, 1811, in Independence, Conn.