Budd, Lucy (2007). "Global networks before globalisation: imperial airways and the development of long-haul air routes". GaWC Research Bulletin. Loughborough University. hdl:2134/4666. S2CID126716007.
Budd, Lucy (2007). "Global networks before globalisation: imperial airways and the development of long-haul air routes". GaWC Research Bulletin. Loughborough University. hdl:2134/4666. S2CID126716007.