1. mr Milen Velushev (2014) "The Need For Differentiation Between Vertical And Horizontal Inward Foreign Direct Investments In Terms Of Host Country National Competitiveness- Evidence From Bulgaria" - REDETE 2014 - Researching Economic Development and Entrepreneurship in Transition Economies
(https://ekonferencije.com/en/paper/the-need-for-differentiation-b/2677)