Volumes 1-49 of The Harvard Classics include reprints of hundreds of authors' works that may have been in the public domain (e.g., because of expired copyrights) or covered by existing copyright holders such as other publishing companies. In either case, Collier filed copyrights for the 49 volumes and for The Harvard Classics complete series in 1909 and 1910 and obtained, when necessary, permission to reprint selected works included in one of the 49 volumes. Collier's copyrighted Volume 50 was in 1910, the "Lectures on The Harvard Classics" in 1914, and "Fifteen Minutes a Day - The Reading Guide" in 1916.