Advertisement
Browse Subject Areas
?

Click through the PLOS taxonomy to find articles in your field.

For more information about PLOS Subject Areas, click here.

< Back to Article

Figure 1.

Flow diagram of the study selection process.

More »

Figure 1 Expand

Figure 2.

Line graph showing the number of studies published per year since 1990.

More »

Figure 2 Expand

Figure 3.

Diagram showing the number of studies conducted in each continent since 1990.

More »

Figure 3 Expand