1: Marshal Alfred (1921), ‘Industry and Trade’, pp.423.
2:Government of India, planning commission, Tenth five year plan (2002-07), VOL II, pp.931
3: Pant (1945), ‘Transport Problems in India’, Hind Kitab Publishers, Bombay, pp.10.
4: Das (1984), ‘Organization and Management of Road Transport’, A Dissertation submitted to Utkal University, Orissa, pp.246.