The 50 volumes were first printed in 1909 (first 25 volumes) and 1910 (next 25 volumes), and the collection was subsequently expanded when the "Lectures on The Harvard Classics" was added in 1914 and "Fifteen Minutes a Day - The Reading Guide" in 1916. The "Lectures on The Harvard Classics" was edited by Willam A. Neilson who also assisted Eliot in the selection and design of the included works in Volumes 1–49. Neilson also wrote the introductions and notes to the included selections in Volumes 1–49. The Harvard Classics is often (mistakenly) cited as a "51 volume" set; however, P.F. Collier & Son consistently marketed the Harvard Classics as 50 volumes plus Lectures and a Daily Reading Guide. Both "The Harvard Classics" and "The Five-Foot Shelf of Books" are registered trademarks of P.F. Collier & Son for a series of books used since 1909.