1] Stefan Ninkovic The possibility of development of organic agriculture in Herzegovina" - II međunarodni simpozijum i 18-to naučno-stručno savjetovanje agronoma Republike Srpske, 30.01.2013.
(https://ekonferencije.com/sr1/rad/the-possibility-of-development/1897)

2] Stefan Ninkovic THE POSSIBILITIES OF JUINT ACTION OF PRODUCERS OF MEDICINAL HERBS AND HONEY PRODUCERS IN THE MUNICIPALITY OF TREBINJE" - II međunarodni simpozijum i 18-to naučno-stručno savjetovanje agronoma Republike Srpske, 29.01.2013.
(https://ekonferencije.com/sr1/rad/the-possibilities-of-juint-act/1886)