Other

‘Reducing Emissions from non-road spark ignition engines and equipment: Decision regulation impact statement 2016’, Department of Environment and Energy, Australian Government.
http://www.environment.gov.au/protection/air-quality/non-road-spark-ignition-engines-and-equipment

The American Green Zone Alliance - providing education, awareness, certification and accreditation in zero-emission landscape maintenance strategies.
https://www.agza.net