Recent research on expert teachers suggests that an integrated understanding across the core domains of teachers' knowledge is crucial for their professional competence. However, in initial teacher education pre-service teachers seem to struggle with the integration of knowledge represented in multiple domain-specific sources into a coherent structure (e.g., textbooks that focus either on content knowledge, on content-specific pedagogical knowledge, or on general pedagogical knowledge). The purpose of this study was to investigate the effectiveness of writing tasks (unspecific vs. argumentative) and prompts (i.e., focus questions) on pre-service teachers' construction of a mental model that interrelates information from multiple domain-specific documents. Data of ninety-two pre-service teachers, who participated in a laboratory experiment where they read three domain-specific textbook excerpts and wrote essays for global comprehension, were analyzed using automated structural and semantic measures. In line with prior research, results indicated that prompts supported pre-service teachers in integrating domain-specific knowledge from multiple documents in their mental models. However, the automated structural and semantic measures did not support previous findings on the efficacy of argument tasks for knowledge integration. The findings and limitations are discussed, and conclusions are drawn for future research and for integrative learning environments in pre-service teacher education.