When traveling, especially internationally, certain physical or digital "papers" are required for entry and identification:

It is highly recommended by the U.S. Department of State to keep physical copies of your documents separate from the originals and to save digital photos on your phone. 2. Academic & Research Papers

Other acceptable forms include a U.S. Passport Card , Permanent Resident Card , or a REAL ID-compliant driver's license for domestic flights.

If you are looking for scholarly research, recent studies explore how travel affects psychology, the environment, and urban planning:

For documenting journeys through scrapbooking or journaling, these paper products are popular options: International Travel Checklist | Travel.State.gov