Luke describes his sources for Luke and Acts in the Gospel of Luke, chapter 1. People in Luke's culture primarily relied on oral tradition to preserve and pass down accurate accounts of historical events. Students were responsible for preserving the thoughts of their teachers. Mnemonic skills were widely practiced and highly valued. Jesus probably spoke mostly in Aramaic but his sayings were likely translated early into Greek. Luke was probably able to interview eyewitnesses during his travels with Paul. He also used documents that were already written and stories that were widely known. Archeaology confirms Luke's geographical and historical references.