"Version: 20210601"--Title page verso.Includes bibliographical references.1. Introduction -- 2. Basics of stellar magnetic field studies -- 2.1. Introduction to the field -- 2.2. The Stokes formalism -- 2.3. The oblique rotator model -- 2.4. The zeeman effect -- 2.5. Broad-Band linear polarisation -- 2.6. Magnetic field modulus -- 2.7. Autocorrelation -- 2.8. Spectral line moments in Stokes I a…