sentences:  During 1957, Bristow Helicopters received a contract from British Petroleum, which allowed the firm to purchase its own helicopters, a pair of Westland Widgeons.That same year, having realised that few companies could afford helicopter services, Bristow began to seek work around the globe; the company soon launched successful ventures into both Iran and Bolivia.In 1960, Bristow Helicopters chose to enter the African market via the acquisition of crop-spraying specialist "Fison-Airwork", which had also operated in locations in Central America and the UK.