1. AHDB 2014 Encyclopaedia of Pests and Natural Enemies in Field Crops https://potatoes.ahdb.org.uk/publications/encyclopaedia-pests-and-natural-enemies-field-crops
2. Alberta Agriculture and Forestry 2014 Economic Thresholds for Insects Attacking Cereals and Corn http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm2474#25
3. Occurrence and population density of aphids in apple orchards of south Bulgaria;Andreev;Journal of Plant Protection Research,2013
4. Defra 2016 Farming Statistics. Final Crop Areas and Cattle, Sheep and Pig Populations at 1 June 2016 - England https://www.gov.uk/government/statistics/farming-statistics-final-crop-areas-and-cattle-sheep-and-pig-populations-as-at-1-june-2016-england
5. Crop loss assessment on winter wheat attacked by the grain aphid Sitobion avenae (F.);George;Plant Pathology,1979