1. Alford DV (2014) Pests of fruit crops: a colour handbook, 2nd edn. CRC Press, Boca Raton, pp 71–72.
https://books.google.com/books?id=XZPSBQAAQBAJ&pg=PA71
). ISBN 978-1-4822-5421-1
2. Alston D (2007) Pear psylla (Cacopsylla pyricola). Utah State University Extension and Utah Plant Pest Diagnostic Laboratory, Logan
3. Anonymous (1979) Integrated pest management of insects and mites attacking pears in southern Oregon. Agricultural experiment station bulletin, vol 634. Oregon State University, Corvallis, pp 19–20
4. Anonymous (1988) Tree fruit crops. Cornell Cooperative Extension, Ithaca, pp 1–2
5. Anonymous (2003a) Rosy apple aphid. UK Cooperative Extension Service, University of Kentucky-College of Agriculture, Lexington, pp 1–2