several possible answers. If the answer to a problem is correct, the reader moves on to the next problem. If the answer is incorrect, the reader is given feedback and is asked to pick a different answer. This educational technique would form a basis for many later narrative gamebook series. During the 1960s, authors from several different countries started experimenting with fiction that contained multiple paths and/or endings. Some literary works in this vein include the French-language novel L'ironie du sort (1961) by Paul Guimard, the Spanish-language novels Hopscotch (1963) by Julio Cortázar and Juego de cartas (Card Game, 1964) by Max Aub, and the works of the French literary group known as the Oulipo (1967). Other early experiments include the short stories "Alien Territory" and "The Lost Nose: a Programmed Adventure" (both 1969) by John Sladek, the novel The French Lieutenant's Woman (1969) by John Fowles, and the collection of short stories titled Tante storie per giocare (Many Tales to Play With, 1971) by Italian author Gianni Rodari. Taken together, these influences may have contributed to the development of several pioneering gamebooks in the 1960s and 1970s. These include Lucky Les by E.W. Hildick (1967), State of Emergency by Dennis Guerrier and Joan Richards (1969), the Swedish-language book Den mystiska påsen (The Mysterious Bag, 1970) by Betty Orr-Nilsson, and the French-language book Histoires comme tu voudras (Stories as You Want Them, 1978) by Marie-Christine Helgerson, among others. Breakthroughs and popularization The first gamebook series proper appears to have been Tracker Books, published by Transworld in the UK between 1972 and 1980. This series includes adventures in a variety of genres such as science fiction, mystery, and sports. Meanwhile, in the US, The Adventures of You series appeared in 1976–77, with two titles that would later become part of the groundbreaking Choose Your Own Adventure series: Sugarcane Island by Edward Packard and Journey Under the Sea by R. A. Montgomery. Tabletop role-playing games such as Dungeons & Dragons were another early influence that would contribute in major ways to the development of the gamebook form. The first module which combined a branching-path narrative with a set of role-playing game rules was Buffalo Castle for the Tunnels & Trolls system (1975). Buffalo Castle was innovative for its time, as it allowed the reader to experience a role-playing session without need for a referee. It has been followed by many other solitaire