This study used think-aloud methodology to explore undergraduates' spontaneous attention to and use of source information while reading six documents that presented conflicting views on a controversial social scientific issue in a Google-like environment. Results showed that students explicitly and implicitly paid attention to sources of documents as well as sources cited within documents and that their attention to source information was associated with its use in evaluating, predicting, and interpreting the content of the documents. Students' sourcing activity varied across documents. The two documents that took the strongest, opposing stances on the controversy elicited the most sourcing. We also observed that, in essays they wrote on the controversy, students' spontaneous sourcing activity was related to their citation of a particularly trustworthy source. The study's theoretical implications are discussed in terms of the Documents Model framework. (Contains 4 tables and 1 figure.)