6Seppo A. Niemi, Tommi P. J. Paanu, Mika J. Lauren. Effect of Injection Timing, EGR and EGR Cooling on the Exhaust Particle Number and Size Distribution of an Off- Road Diesel Engine. SAE 2004 -01 - 1988.
7F. Millo, F. Mallamo, L. Amone-Lombardini. Analysis of Different Internal EGR Solutions for Small Diesel Engines. SAE 2007 - 01 - 0128.
8Kazuo Fujihara, Yamato Nakamizo, Mitsuru Kojima, et al. , Development of an NO, Reduction System Using Exhaust Valve Controls in Small Engines for Motorcycles. SAE 2009 - 32 - 0043, SETC 2009.
