Bildquellennachweis

museum © Olaru Radian / Fotolia.com
Buch im Regal © Robert Kneschke / Fotolia.com
Dark background with books © Denis Mironov / Fotolia.com
database concept. vintage cabinet. library card or file catalog. © Andrey Kuzmin / Fotolia.com
Gute Research © mediaphotos/istockphoto.com