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. 2013 Sep 23;12:81. doi: 10.1186/1476-069X-12-81

Figure 1.

Figure 1

Path diagrams of the structural equation models. (A) The effect of traffic pollution on parasympathetic tone. (B) The effect of traffic pollution on sympathetic tone marker, LF/HF. Ellipses are used to denote latent constructs, rectangles are used to denote the observed variables measuring and affecting these constructs, and single-headed arrows are used to denote directional relationships, from predictor to outcome.