NITROUS OXIDE (NOx) REDUCTION SYSTEMS FOR EXHAUST SYSTEMS BEING PARTS OF INTERNAL COMBUSTION ENGINES, COMPRISED OF SELECTIVE CATALYTIC REDUCTION (SCR) CATALYSTS AND HOUSING THEREFOR, REDUCTANT DOSING UNITS AND NOZZLES, CONTROL UNIT PANELS, SENSORS, WIRING HARNESSES AND ON-BOARD DIAGNOSTIC DEVICES FOR THE REDUCTION AND ELIMINATION OF ATMOSPHERIC NOx, SOLD AS A UNIT