1) Chancellor, W. J. and N. C. Thai: Automatic control of tractor transmission ratio and engine speed, Trans. of the ASAE, Vol. 27, No. 3, p. 642-646, 1984
2) Horst Göhlich and Johann-Carste Kipp: New aspects in tractor development and design, The Proceedings of International Symposium on Agricultural Mechanization and International Cooperation in High Technology Era, Tokyo, p. 149-157, 1987