NEW YORK -- Lawrence S. Ritter, who wrote the baseball classic "The Glory of Their Times," died at the age of 81.

Ritter had a series of strokes and died at his apartment in New York, according to Marty Appel, a regular at Ritter's monthly gathering of baseball writers.

"The Glory of Their Times" was published in September 1966 for a $3,000 advance, according to Appel. Ritter, accompanied by his son, spent four years with a reel-to-reel tape recorder gathering oral histories from baseball players from the early part of the 20th century, telling first-person accounts of Ty Cobb, John McGraw, Honus Wagner, Rube Marquard and Smoky Joe Wood in the early 1900s.

Twenty-two players were interviewed, and Ritter divided the royalties among the players and their familiar. The book has sold more than 400,000 copies, according to Appel, and PBS aired a broadcast based on the book in 1975. A CD of the interviews also was released.

Ritter, a graduate of Indiana University, received a doctorate from the University of Wisconsin. He became a professor of finance at NYU for more than 30 years, becoming chairman of the business school's finance department, where there is a research room and an endowed chair in his name.

With Gregory Udell and William Silber, he was the author of "Principles of Money, Banking and Financial Markets," first published in 1974 and now in its 11th edition.

In addition to "The Glory of Their Times," Ritter wrote "Lost Ballparks," "The Babe: A Life in Pictures" (with Mark Rucker), "The Story of Baseball," "The Image of Their Greatness" (with Donald Honig), "East Side, West Side: Tales of New York Sporting Life," "The 100 Greatest Baseball Players of All Time" (with Honig) and "Leagues Apart: The Men and Times of the Negro Baseball Leagues."

He is survived by his son, his brother, and one granddaughter.