A. J. Fajardo Quesada, E. A. Hernández González, R. Herrero Pacheco, and L. V. Beritán Yero, “Chapter 7. Heat maps: representing research density”, in Applied bibliometrics. From data to publication (Spanish Edition), AG Editor, 2025, pp. 109–114. doi: 10.62486/978-9915-9680-6-3.ch07.