 Complete the following phrase:  At the DBR4s World Championship debut in the 1959 Dutch Grand Prix on 31 May, Shelby and Salvadori could only manage 10th and 13th fastest in qualification, respectively. During the race both cars succumbed to engine problems in the early laps and failed to finish. Further delays and shifted priorities meant that the light green Astons only appeared at a further three races of the 1959 Formula One season. The DBR4s failed to score even a single point during this time; their best results being a pair of 6th places for Salvadori, taken at the British and 