Empirical Research (Primary Sources): Studies that are based on observations or experiments. Clinical trials, case studies, and most meta-analyses are empirical research.
Literature Review (Secondary Sources): Articles that summarize the research in a particular subject or topic. They often include a summary, a systematic review, and meta-analyses.
Case Study (Primary Sources): Articles that provide real cases from clinical practice. They often include descriptions of symptoms and diagnosis.
Clinical Trial (Primary Sources): Studies that are often based on large cohorts of people. They often include descriptions of methodology and control groups.
Opinion Paper: Papers of opinions that often include personal thoughts, beliefs, feelings, or a judgement or conclusion based on facts. Their goal may be to persuade or influence the reader.
Book Review: Papers of opinions that critique recent publications in the field. They tend to be brief and to the point.