Markič, Miloš, and Tjaša Kanduč. “Carbon Isotopic Composition of Methane and Its Origin in Natural Gas from the Petišovci-Dolina Oil and Gas Field (Pannonian Basin System, NE Slovenia) – a Preliminary Study”. Geologija, vol. 65, no. 1, July 2022, pp. 59-72, https://doi.org/10.5474/geologija.2022.004.