Fig. 5
From: Bibliometric analysis of cardiometabolic disorders studies involving NO2, PM2.5 and noise exposure
Word clouds for the signature index keywords for references involving (a) NO2, (b) PM2.5, (c) Noise, (d) NO2 + PM2.5, (e) NO2/PM2.5 + noise. Font size and color of a term is proportional to its relatively frequency and we use black, dark grey and light grey to indicate the relative frequency over 20, 10–20% and less than 10%, respectively