Figure 5 (A, C) The co-occurrence network and the clusters of keywords on HM. Keywords sharing a common color are part of the same cluster. A denser line between keywords suggests a higher probability of their concurrent appearance in a single article. In Figure 5C, keywords in yellow indicate proximity to the article’s publication year, whereas those that are purple have greater temporal distance from it. Threshold: A minimum of 25 occurrences for a keyword and a clustering resolution of 1.3. (B, D) Co-cited reference timeline map of publications on HM. In Figure 5B, the color gradient from purple to yellow signifies the average year of keyword occurrence, transitioning from distant to recent. In Figure 5D, keywords in yellow are nearer to the article’s publication year, while those in purple suggest a greater temporal distance from it. (A, B) Produced using CiteSpace (version 6.2.R2, Drexel University, Philadelphia, USA), (C, D) produced using VOSviewer (version 1.6.19, Leiden University, Leiden, Netherlands).