Scholarly work is not always done in monograph, or book length, format. Often you will find the information you seek about a topic, such as the Donnellys, in a journal article. For instance, Bruce Elliott has written a journal article about the origins of James and Johannah Donnelly. Historians write journal articles rather than books for a number of reasons. Sometimes the topic of an article does not warrant an entire book. Other times, the journal article is part of what might later become a full-length book. It is often helpful to read journal articles because they typically provide a short but informative introduction to a topic. Alternatively, journal articles can also provide readers with more in-depth coverage of a specific aspect of a topic, as does Elliott in the example described above.
Articles that appear in academic journals, as opposed to magazines, are peer-reviewed. This means that other experts in the field examine them for their scholarly merit prior to accepting them for publication. Also, journal articles in the field of history are almost always written using primary documents. Magazine articles are usually written by consulting other secondary sources, and are generally authored by a journalist or commentator rather than an expert in the field. Yet, just because an article in a journal is printed and peer reviewed does not mean that it is true. Just like books, articles in journals have to be examined and interrogated critically. Few scholarly articles are written about the Donnellys or their murders.
Journal articles can be found electronically by accessing databases that index them or by consulting the indexing tools at the library.