Bernal, M. S. M. (2013). Productivity and competitiveness determination of the small-scale mining at the northern mining district in the state of Boyacá. Universidad Pedagógica y Tecnológica de Colombia.
Lua i Stíl Chicago (17ú heag.)Bernal, Martha Stella Martínez. Productivity and Competitiveness Determination of the Small-scale Mining at the Northern Mining District in the State of Boyacá. Universidad Pedagógica y Tecnológica de Colombia, 2013.
Lua MLA (9ú heag.)Bernal, Martha Stella Martínez. Productivity and Competitiveness Determination of the Small-scale Mining at the Northern Mining District in the State of Boyacá. Universidad Pedagógica y Tecnológica de Colombia, 2013.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.
