While primary sources are essential, secondary and tertiary sources are invaluable to a researcher. While it is true that they are one or more steps removed from the primary sources—the raw data that informs them— there is a huge difference between an academic, peer-reviewed analysis about period dyeing practices in Japan and a Wikipedia article on the history of dyeing.
To clarify our terms for a moment, secondary sources are one step removed from the artifacts and the people who used them. Usually, but not always, these are academic articles written by scholars and are focused on a particular, narrow subject, such as a specific archaeological dig or a collection of letters written by a particular individual. Secondary sources would also include non-professional papers where people researched and drew conclusions based on a set of artifacts, documents, and/or paintings. While secondary sources usually include photographs of some examples of items being studied and quotes from relevant written sources, their focus is on conclusions based on the study of the artifacts combined with that person’s interpretation of those artifacts etc. within the context of the author’s wider knowledge. While the researcher may draw on some tertiary sources to situate their particular subject within the larger social, political, economic, and historical context that it belongs to, the research is focused primarily on the collection of artifacts themselves.
Tertiary sources, in comparison, are one more remove from the primary sources than secondary sources are, as they are compilations of information drawn from multiple secondary sources. These range in quality from Encyclopedia or Wikipedia entrees to scholarly treatises. Because of their broader scope, they can give a broader analysis than a secondary sources are capable of, such as how pottery trends change in a region through time, or how they vary across a region, or even how they influenced other societies’ pottery along shared trade routes. While tertiary sources still often include some examples of primary sources, their data is primarily drawn from a collection of other scholars’ works, especially secondary sources. They sacrifice a detailed analysis of specific artifacts to focus on bigger picture trends.

Information gained through other venues, ranging from professional conference paper presentations to personal communications, whether in person or via letters or email, are also valid sources of information for your research. In academia, paper presentations are where we can access the most cutting edge of research, as these papers are often presented well ahead of print publications of said research. Personal communications (such as letters, emails, and face to face conversations/interviews) are also not only acceptable resources in academia, but often valuable ones.
My dissertation, for example, was based not only interviews and other interactions with locals affected by the E. coli contamination, but also personal conversations and emails with experts in a variety of positions about information relative to my research. In the Living History organizations, we learn a great deal from others who have been working on related issues, such as an expert who has done extensive research that touches upon our own or a museum curator answering questions about a given artifact. These are, at least in academia, considered valuable sources. Sometimes the Living History groups get a ‘bad rap’ about what they do. This is unfortunate because they are a perfect example of Experimental Archaeology in practice, and their experiments can greatly broaden your research if you get the chance to talk to them.
It is so easy to heavily prioritize primary sources, in part because primary sources are the most unbiased references we can find. As a result of this tendency, however, we disregard or even penalize non-academic researchers who draw heavily on secondary and especially tertiary sources. In academia, while primary sources are still considered both an incredibly valuable and a fundamental part of research for many of the same reasons they are in other organizations, quality secondary and even tertiary sources are also respected.
In this new age of instant gratification of the the information highway, Academia now accepts internet sources. Just be sure to learn to vet all of your your source as there are many things that factor into whether or not a source is considered a quality source, including the training background of the researcher, how the research itself was conducted, the sources cited within the document, which the publisher it is, and whether or not that source was peer reviewed. Peer review means that a group of people trained in the same field, such as archaeology or history, has read and approved of the work presented in the paper. Most often, peer reviewed sources are either published by academic publishers or in academic journals, though they can also include papers presented at professional conferences, websites hosted by respected institutions, and other, less traditional sources.
All of these things help you build your research on your topic, allowing you to create a balanced foundation of knowledge to support your thesis. A good research paper, will have a balance of Primary, Secondary, and Tertiary sources cited in the bibliography.
RoseAnna
The Researcher’s Gateway