l have a Garden Concert Programme from April 12, 1913, honoring Andrew Carnegie’s 25th year as President of the New York City Oratorio Society. It is signed by Andrew Carnegie, Louise W. Carnegie (his wife), and conductor Louis Kommenich. I would appreciate guidance on how to determine a value and market for this item. Item is in good condition, has ribbon tie on top, edges are tanned; autographs are clear and legible.