When you cite the name of a book which has both a title and a subtitle, separate the two with a colon. Do this even though no colon may appear on the cover or the title page of the book itself.
Human Towers:A Catalan Tradition
Ratios
Ratios can be written with words (two to one) or with numbers and a colon (2:1).
«Other uses» [en línia]. A: Llibre d’estil de la Universitat de Barcelona. Barcelona: Universitat de Barcelona. Serveis Lingüístics. <https://www.ub.edu/llibre-estil/criteri.php?id=2294> [consulta: 21 novembre 2024].