In many situations, readers are asked to learn from multiple documents. Many studies have found that evaluating the trustworthiness and usefulness of document sources is an important skill in such learning situations. There has been, however, no direct evidence that attending to source information helps readers learn from and interpret a document's content. In this study we examined whether students' awareness of sources predicts their comprehension of documents, controlling for prior knowledge, interest and perceived comprehensibility of the texts. Participants read multiple texts that provided different perspectives on the causes and solutions of climate change. Deep comprehension was measured using both within-text and across-text inference verification tests. Source awareness was measured using a test of memory for sources. We found that memory for sources predicted both types of deep comprehension. These results, in combination with source training studies, suggest that improving students' sourcing skills may benefit their learning of text content. (Contains 3 tables.)