F5: Dangling Modifiers: Don’t leave out the word or words you intend to modify, or your modifier will dangle ridiculously. See Writing for Success Section 2.7 pp. 94-95 or the following: http://grammar.ccc.commnet.edu/grammar/modifiers.htm
While walking across campus, the books felt they weighed fifty pounds.
(Incorrect) — We don’t know who was walking. It reads like the books were walking.
While walking across campus, Delores felt the books weighed fifty pounds.
(Correct) — The proper noun was added for the opening phrase to modify.