1. Defra 2005 UK non-native organism risk assessment scheme. User manual www.nonnativespecies.org/downloadDocument.cfm?id=158
2. EPPO 2011a EPPO Decision-support scheme for quarantine pests. EPPO Standard PM 5/3(5) http://archives.eppo.int/EPPOStandards/PM5_PRA/PRA_scheme_2011.doc