Tertiary-level English as a foreign language (EFL) learners in Taiwan are often required to read English-medium textbooks in their disciplinary courses. In science and engineering, it is a common practice for teachers to assign students English text but lecture in the local language, Chinese. In this study, we provided a situated picture of how these students interact with the text in their disciplinary context by triangulating multiple knowledge sources available to them. This includes analysis of the subject textbook in L2 (English), lectures in L1 (Chinese), and artifacts produced in the class, such as syllabus, exam sheets, and students' notes. Semi-structured interviews were conducted to investigate the students' and an instructor's perceptions of the role of these sources and their interrelationships. The findings reveal that students exploited various meaning-making resources to comprehend the ideas covered in the textbook. In addition, the instructor's explanation of the teaching materials, homework problem sets, and exam questions all proved to be important and interconnected resources that students rely on in their reading practices. Notably, problem sets and equations captured the students' attention while reading the textbook. We discuss the role of problem sets in scientific textbooks and suggest implications for further research.