In order for the event mentions to be useful (i.e., for knowledge extraction tasks), it is important to determine their factual certainty so the actual event mentions can be retrieved (i.e., the event factuality prediction problem (EFP)). In this work, we focus on the recent regression formulation of EFP that aims to predict a real score in the range of [-3,+3 ] to quantify the occurrence possibility of a given event mention (Stanovsky et al., 2017;<cite> Rudinger et al., 2018)</cite> .