Question: Sparring with Hemingway was a book that included bouts with the undisputed champion of what weight class from 1980 to 1987?
Context: The Bellator MMA (formerly known as "Bellator Fighting Championships") promotion was started in 2008 by Bjorn Rebney and Brad Epstein as a tournament based alternative to other MMA organizations such as the Ultimate Fighting Championship and Strikeforce.  Prior to 2015, when president Scott Coker made the decision to drop the 8-man tournament format, Bellator fighters participated in a series of tournament bouts in a set weight class over a season (usually between 10 and 13 events over 3 or 4 months).  The winners of these tournaments were crowned Bellator champions, with the winners of successive tournaments in the same weight class earning the spot of no. 1 contender. K-1 World MAX 2005 Championship Final was a kickboxing event promoted by the K-1 organization.  It was the fourth K-1 World MAX final for middleweight kickboxers (70 kg/152 lb weight class), involving eight finalists and two reserve fighters, with all bouts fought under K-1 rules.  All eight of the finalists had won elimination fights at the K-1 World MAX 2005 World Tournament Open, while the reserve fighters were invited despite suffering defeats.  As well as tournament matches there were also three super fights fought under K-1 rules (70 kg/152 lb weight class).  In total there were sixteen fighters at the event, representing nine countries. In professional boxing, the undisputed champion of a weight class is a boxer who is recognized as the world champion at that class by each boxing organization. Marvelous Marvin Hagler (born Marvin Nathaniel Hagler; May 23, 1954) is an American former professional boxer who competed from 1973 to 1987.  He reigned as the undisputed middleweight champion from 1980 to 1987, making twelve defenses of that title, and currently holds the highest knockout percentage of all undisputed middleweight champions, at 78%.  At six years and seven months, his reign as undisputed middleweight champion is the second longest of the last century, behind only Tony Zale, who reigned during World War II.  In 1982, annoyed that network announcers often did not refer to him by his nickname, "Marvelous", Hagler legally changed his name to Marvelous Marvin Hagler. In professional wrestling, a weight class is a standardized weight range for the wrestlers.  The top class in almost every promotion is heavyweight, but super heavyweights exist.  Weight class matches in modern-day American professional wrestling are rare, but weight class championships still exist.  However, Japanese professional wrestling, Mexican wrestling and British wrestling use the weight classes more seriously. In taekwondo, a weight class is a standardized weight range for taekwondo practitioners.  The upper weight limit for each class is the lower limit of the next highest class.  A taekwondo gyeorugi is usually scheduled for a fixed weight class, and each practitioner's weight must not exceed the upper limit. Sparring with Hemingway is a book written by Budd Schulberg consisting of a collection of Schulberg's articles on boxing spanning nearly half a century.  The book includes descriptions of fights between Marciano and Archie Moore; Ali and Foreman; Leonard and Duran; and Hagler and Hearns.  A review of the book in the "New York Times" praises Schulberg's technical expertise on the subject of boxing.  A "Chicago Tribune" review of the book states: The pieces in the present volume range over the whole of Schulberg's career and include those drawn from his days as a reporter for the New York Post as well as assignments for Sports Illustrated and other publications.  He chronicles the demise of Archie Moore, the implacable assaults of Rocky Marciano, the supernova-like appearance of Cassius Clay and his psych job on the theretofore-invincible Sonny Liston, the saga of Mike Tyson (predicting long before Tyson's conviction on rape charges that "the biggest fight of all may still be Tyson vs. Tyson") and the resurrection of George Foreman: "Win or lose, this 260 pounds of fighting preacher has proved what . . . F. Scott Fitzgerald denied when he wrote, `There are no second acts in American lives.' " In combat sports where champions are decided by a challenge, the lineal championship of a weight class is a world championship title held initially by an undisputed champion and subsequently by a fighter who defeats the reigning champion in a match at that weight class.  In professional boxing, the lineal champion is informally called "the man who beat the man".  Champions recognized by sanctioning bodies such as the World Boxing Association (WBA) or World Boxing Council (WBC), or the Ultimate Fighting Championship (UFC) may vacate their title voluntarily, or be stripped of the title for breaching the sanctioning body's regulations or contracts.  There will thus be a breach of continuity in the list of sanctioned champions which the lineal championship is intended to prevent.  However, there is no single canonical list of lineal champions at any weight class, because there is no agreed upon method of determining the starting point for each lineage and conflicting opinions on what to do when the current champion retires or moves to a different weight class, although there is agreement that any stripping of a title be discounted. A weight class is a measurement weight range for boxers.  The lower limit of a weight class is equal to the upper weight limit of the class below it.  The top class, with no upper limit, is called heavyweight in professional boxing and super heavyweight in amateur boxing.  A boxing match is usually scheduled for a fixed weight class, and each boxer's weight must not exceed the upper limit.  Although professional boxers may fight above their weight class, an amateur boxer's weight must not fall below the lower limit.  A nonstandard weight limit is called a catch weight. Charles Henry "Jack" Blackburn (May 20, 1883 – April 24, 1942) was an American boxer and boxing trainer.  Fighting in the first half of his career as a lightweight and later a welterweight, he was known for an exceptional defense and fought many men above his weight class, including six bouts with the great Sam Langford.  He fought Joe Gans three times in no-decision bouts, defeating him once according to newspaper accounts and made good showings against Harry Lewis, Philadelphia Jack O'Brien, and Harry Greb.  He found most of his fame training 1937 World Heavyweight Champion Joe Louis, but also had a significant role in training 1926 Lightweight Champion Sammy Mandell.  He helped to train World Bantamweight Champion Bud Taylor and World Light-Heavyweight Champion John Henry Lewis.
Answer: middleweight