Digital humanities entail applying computational tools and methods to traditional humanities research. In this paper, we focus on history, which can be seen either as part of humanities or social sciences research. We approach the subject from the point of view of digital methods in humanities research and information retrieval. The purpose of this study is to explore the themes emerging in the recent literature concerning historians' changing work tasks in the digital era. We present a literature review based on a careful inspection of the focused sample of 47 conference/journal articles discussing digital humanities from the point of view of historical research and information retrieval. The results illustrate the requirements and needs of historians working with recent technology, the types of data discussed in the literature, and technologies and tools available to answer historians' needs. We observe and report recurring themes in the literature in order to give an overview of the subject.