Final answer:
Company newsletters and academic journals, which may contain personal bias, are classified as secondary sources because they provide analysis based on primary data.
Step-by-step explanation:
Data that may contain personal bias like company newsletters and academic journals are considered secondary sources. Secondary sources rely on other sources rather than direct observation or firsthand experience. This category includes books, articles, and texts that provide perspective and analysis based on primary sources. For instance, a company newsletter may interpret and summarize internal events, and an academic journal might analyze or discuss previous research, thus providing a second layer of interpretation over the primary data.
When trying to distinguish between types of sources, remember that primary sources include firsthand accounts and original documents, whereas tertiary sources often summarize or condense information from primary and/or secondary sources. Items such as encyclopedias and bibliographies are examples of tertiary sources. Hence, in the context of the options provided, academic journals and company newsletters, which typically contain bias or perspective based on the interpretation of original events or data, would be classified as secondary sources.