**F5089a.71 Foster, Samuel, professor of astronomy in Gresham
college. -1652.
The sector altered and other scales added: with the description and use thereof. Invented and written by Samuel Foster. And now published by W. L(ybourn). London: pr. by A. Clark. 1673. (In Gunter, Edmund. Works. 5th ed. Pp.» 157-195. London, 1673.)
-Sector. -Quadrant. aa