Porter, Michael (1976-12-01). "Please Note Location of Nearest Exit: Exit Barriers and Planning". California Management Review. 19 (2): 21–33. doi:10.2307/41164693. JSTOR41164693. S2CID154746142.
Eaton, Curtis; Lipsey, Richard (1980). "Exit Barriers are Entry Barriers: The Durability of Capital as a Barrier to Entry Author". The Bell Journal of Economics. 11 (2): 721–729. doi:10.2307/3003391. JSTOR3003391.
Porter, Michael (1976-12-01). "Please Note Location of Nearest Exit: Exit Barriers and Planning". California Management Review. 19 (2): 21–33. doi:10.2307/41164693. JSTOR41164693. S2CID154746142.
Eaton, Curtis; Lipsey, Richard (1980). "Exit Barriers are Entry Barriers: The Durability of Capital as a Barrier to Entry Author". The Bell Journal of Economics. 11 (2): 721–729. doi:10.2307/3003391. JSTOR3003391.