Recent research has mainly used two approaches to identify publishers or sources of disinformation: First, alternative media are identified as potential publishers of disinformation. Second, potential publishers of disinformation are identified via fact-checking websites. Samples created using those approaches can partly overlap. However, the two approaches differ in terms of validity and comprehensiveness of the identified population. Sampling of alternative media outlets is theory-driven and allows for cross-national comparison. However, researchers face the challenge to identify misinforming content published by alternative media outlets. In contrast, fact-checked content facilitates the identification of a given disinformation population; however, fact-checker often have a publication bias focusing on a small range of (elite) actors or sources (e.g. individual blogs, hyper partisan news outlets, or politicians). In both approaches it is important to describe, compare and, if possible, assign the outlets to already existing categories in order to enable a temporal and spatial comparison.