1. Hierarchical Task Analysis (HTA)
2. CAA. (2011).CAA “Significant seven” task force reports. CAA paper 2011/03.https://publicapps.caa.co.uk/docs/33/2011_03.pdf
3. CAA. (2014).Safety Notice SN–2014/004 Level Busts: Hazards and defences. Retrieved January 6 2020 fromhttps://publicapps.caa.co.uk/docs/33/SafetyNotice2014004.pdf
4. CAA. (2016). CAP 413: Radiotelephony manual.https://publicapps.caa.co.uk/docs/33/CAP413MAY16.2.pdf
5. CAA & NATS. (2014).CAP 1186 Level Busts—Information for pilots and controllers. Retrieved January 6 2020 fromhttp://publicapps.caa.co.uk/docs/33/CAP1186LevelBustleaflet.pdf