1 Subjects: “...Spark ignition engines / Alternative fuels...”

2 Subjects: “...spark ignition engine...”

3 Subjects: “...spark ignition engine...”

4 Subjects: “...Spark ignition engines / Alternative fuels / http://id.loc.gov/authorities/subjects/sh85067335...”

5 Subjects: “...exhaust emissions and spark-ignition engine...”

6 Subjects: “...spark-ignition engine...”

7 Subjects: “...Spark ignition engines / Methodology / Analysis...”