1. McDougall P (2015) AgriService: companies section—2014 market situation. Phillips McDougall-AgriService
2. McDougall P (2015) AgriService: products section—2014 market. Phillips McDougall-AgriService
3. Knudsen GC (1988) US4762551
4. Bristow JT (2016) WO2016197900A1
5. Brown SM (1999) Rawlinson H. US5886231