ud2.addUnit(new Unit(-3, Unit.Kind.MOLE, level, version));
ud2.addUnit(new Unit(-3, Unit.Kind.LITRE, -1, level, version));
System.out.printf("\n%s * %s\t=\t", UnitDefinition.printUnits(ud, true), UnitDefinition.printUnits(ud2, true));
ud.multiplyWith(ud2);
ud.simplify();
System.out.println(UnitDefinition.printUnits(ud, true));
ud = new UnitDefinition(level, version);
ud.addUnit(new Unit(18, Unit.Kind.JOULE, 6, level, version));