Based on naming conventions and archival research, here are the most likely possibilities:
Check file properties if you have the PDF but can’t open it: right-click > Properties > Details to see original author or source. Radomir Ilic - Ibar.pdf
Ибар : антропогеографска проучавања Радомира М. Илића. Радомир М. Илић, Radomir M. Ilić. сепарат | штампана грађа | српски | 1905] COBISS.net Based on naming conventions and archival research, here
In the absence of concrete information about Radomir Ilic and his intentions, several theories have emerged to explain the purpose and significance of the "Radomir Ilic - Ibar.pdf" document: Radomir Ilic - Ibar.pdf