Martin, Mike (2014). An Intimate War: An Oral History of the Helmand Conflict, 1978–2012. Oxford University Press. p. 321. ISBN978-0199387984. Consultado el 26 de julio de 2016. «In Pushtun folklore, Barak, Alak and Popol were brothers who went their separate ways to found tribes in their own namesake with the addition of the—zai (son of) suffix, for example, Barakzai.»
