Warrendale, Pa.: Society of Automotive Engineers. ISBN 1-56091-240-5. ↑ Dugald Clerk, "Gas and Oil Engines", Longman Green & Co, (7th Edition) 1897, pp 3-5. ↑ Dugald Clerk, "Gas and Oil Engines", Longman Green & Co, 1897. ↑ "The Historical Documents". Barsanti e Matteucci.