Before the digital age, most research was conducted in the library using books and other paper-based resources. While books are still used for some secondary research, the amount of paper bound research has decreased dramatically as the popularity of the Internet grew. Some books, however, are not available online and the information in them must be obtained through using the paper bound copies.
Many clinicals studies are published in only paper bound format. Because they are usually written for an educated, niche audience and use technical language there would be little advantage to publishing them in their entirely in digital formats. In some cases, the abstracts may be available online or in word processing formats while the full study is only published on paper or in a periodical.
Magazines, newspapers and newsletters are all often cited in research. While many have online or digital editions, they are rarely found in their full format digitally. This is to encourage consumers to purchase printed copies, but it also sometimes forces researchers to use the paper copies for research.
Microfilm, audio recordings, pictures and printed graphics can also be considered paper bound, even if they are not technically printed on paper. Many libraries have made strides in transferring microfilm and other similar paper bound media to digital formats, but there are still many tools that are only available in paper bound editions.