Question: Which single seater auto-racing formula did 1977 Can-Am season series used

full_context: Document 1: Open-wheel car: An open-wheel car (formula car, or often single-seater car in British English) is a car with the wheels outside the car's main body, and usually having only one seat. Open-wheel cars contrast with street cars, sports cars, stock cars, and touring cars, which have their wheels below the body or inside fenders. Open-wheel cars are usually built specifically for racing, frequently with a higher degree of technological sophistication than in other forms of motor sport. Open-wheel street cars, such as the Ariel Atom, are very scarce as they are often impractical for everyday use.
Document 2: 1987 Barber Saab Pro Series: The 1987 Barber Saab Pro Series season was the second season of the series. All drivers used Saab powered BFGoodrich shod Mondiale chassis. Ken Murillo won the championship.
Document 3: Formula One drivers from Canada: There have been thirteen Formula One drivers from Canada, three of whom have scored points. Gilles Villeneuve, rated amongst the greatest drivers of all time, died while qualifying for his 68th race. His son, Jacques Villeneuve won the World Drivers' Championship in 1997. Canadian drivers were absent from Formula One since his departure in 2006, until the arrival of Lance Stroll in 2017, who scored his first career points at the 2017 Canadian Grand Prix.
Document 4: Group 5 (racing): Group 5 was an FIA motor racing classification which was applied to four distinct categories during the years 1966 to 1982. Initially Group 5 regulations defined a Special Touring Car category and from 1970 to 1971 the classification was applied to limited production Sports Cars restricted to 5 litre engine capacity. The Group 5 Sports Car category was redefined in 1972 to exclude the minimum production requirement and limit engine capacity to 3 litres. From 1976 to 1982 Group 5 was for Special Production Cars, a liberal silhouette formula based on homologated production vehicles.
Document 5: 1971 Trans-American Sedan Championship: The 1971 Trans-American Championship was the sixth running of the Sports Car Club of America's Trans-Am Series. The format was altered to an over 2500cc class and an under 2500cc class, up 500cc from past years. All races used split classes except where noted. The year marked the rise of Datsun as a competitive brand, with the Japanese company winning several races throughout the season. American Motors, led by Mark Donohue's 7 wins, and Datsun, led by John Morton's 6 wins, won the manufacturers' championships.
Document 6: 1977 Can-Am season: The 1977 Can Am season was the tenth running of the Sports Car Club of America's prototype-based series. Despite the revived name, however, the new series was entirely unrelated to the previous series which had folded in 1974. This series used Formula 5000 Lola T332s with fenders added. Patrick Tambay was declared champion, winning six of the nine races that year for Carl Haas. While Lola chassis dominated the series, a Chevrolet powered Schkee DB1 driven by Tom Klausler won the first race at Mont Tremblant. Formula One driver Gilles Villeneuve came in third at Road America in a Wolf. While Chevrolet was not the only engine supplier, they swept the entire season. This season also marked a resurgence of interest in SCCA events, with Can Am accompanying F5000 and the Trans Am Series seeing a mild resurgence in the eighties.
Document 7: Wolf WR1: The Wolf WR1 was a Formula One car built for the 1977 season by the Walter Wolf Racing team. Four examples of the car were produced. The first, completed well before the start of the season, was the WR1. Another two identical cars were built: WR2, finished ahead of the first race; and WR3, ready in March 1977. At the end of the season, a fourth car, WR4, was produced with slight adjustments, and WR1 was remodeled in similar fashion for . The original car was driven exclusively by South African future 1979 World Champion Jody Scheckter in 1977. WR3 and WR4 were also driven by fellow future World Champion Keke Rosberg in the 1978 season.
Document 8: 1975 SCCA/USAC Formula 5000 Championship: The 1975 SCCA/USAC Formula 5000 Championship was the ninth running of the Sports Car Club of America's professional open wheel automobile racing series and the second to be sanctioned jointly by the Sports Car Club of America and the United States Automobile Club. The championship was open to cars complying with the SCCA's 5 litre (305 cid) American stock block engine specifications and to cars complying with the USAC's 161 cid turbocharged, 255 cid DOHC or 320 cid stock block engine regulations.
Document 9: 1974 SCCA/USAC Formula 5000 Championship: The 1974 SCCA/USAC Formula 5000 Championship was the eighth running of the Sports Car Club of America's premier open wheel racing series. It was the first to be sanctioned jointly by the Sports Car Club of America (SCCA) and the United States Auto Club (USAC), and the first to be held under the "SCCA /USAC Formula 5000 Championship" name. Sponsorship by the L&M cigarette brand was not carried forward from the 1973 championship.
Document 10: List of USAC Championship Car seasons: From 1956 to 1978, USAC Championship Car seasons featured the top teams and drivers in U.S. open-wheel racing. Until 1971, the Championship contained road courses, ovals, dirt courses, and, on occasion, a hill climb. Thereafter, the schedule consisted mainly of paved ovals. In 1979, the majority of car owners left USAC to race in the Indy Car World Series, sanctioned by the Sports Car Club of America and CART. This led to a decline in the number of events in the schedule, and by the 1984-85 season, the Championship comprised only one race, the Indianapolis 500. The era of USAC Championship Cars concluded with the formation of the Indy Racing League (IRL) in 1995, which was sanctioned by USAC until June 1997 when the IRL assumed officiating duties after the controversial finish of the 81st Indianapolis 500 and the scoring mistake that marred the following event. The most successful driver in USAC Championship Car history was A. J. Foyt with seven National Championships and four Indianapolis 500 victories. Foyt competed in every season from 1957 to 1992-93.
Document 11: List of Formula One drivers: Formula One, abbreviated to F1, is the highest class of open-wheeled auto racing defined by the Fédération Internationale de l'Automobile (FIA), motorsport's world governing body. The "formula" in the name refers to a set of rules to which all participants and cars must conform. The F1 world championship season consists of a series of races, known as Grands Prix, held usually on purpose-built circuits, and in a few cases on closed city streets. Drivers are awarded points based on their position in each race, and the driver who accumulates the most points over each calendar year is crowned that year's World Champion. As of the 2017 Singapore Grand Prix, there have been 970 FIA World Championship races since its first event, the 1950 British Grand Prix.
Document 12: Formula One: Formula One (also Formula 1 or F1 and officially the FIA Formula One World Championship) is the highest class of single-seat auto racing that is sanctioned by the Fédération Internationale de l'Automobile (FIA). The FIA Formula One World Championship has been the premier form of racing since the inaugural season in 1950, although other Formula One races were regularly held until 1983. The "formula", designated in the name, refers to a set of rules, to which all participants' cars must conform. The F1 season consists of a series of races, known as "Grands Prix" (from French, meaning grand prizes), held worldwide on purpose-built F1 circuits and public roads.
Document 13: 1976 SCCA/USAC Formula 5000 Championship: The 1976 SCCA/USAC Formula 5000 Championship was the tenth running of the Sports Car Club of America's premier open wheel racing series and the third to be co-sanctioned by the Sports Car Club of America (SCCA) and the United States Auto Club (USAC).
Document 14: GP2 Series: The GP2 Series was a form of open wheel motor racing introduced in 2005 following the discontinuation of the long-term Formula One feeder series, Formula 3000. The GP2 format was conceived by Bernie Ecclestone and Flavio Briatore, while Ecclestone also has the rights to the name GP1. In 2010, the GP3 Series class was launched, as a feeder class for the GP2 series. In 2017, the series was rebranded as the FIA Formula 2 Championship.
Document 15: Formula 5000: Formula 5000 (or F5000) was an open wheel, single seater auto-racing formula that ran in different series in various regions around the world from 1968 to 1982. It was originally intended as a low-cost series aimed at open-wheel racing cars that no longer fit into any particular formula. The '5000' denomination comes from the maximum 5.0 litre engine capacity allowed in the cars, although many cars ran with smaller engines. Manufacturers included McLaren, Eagle, March, Lola, Lotus, Elfin, Matich and Chevron.
ground_truth: Formula 5000