Legend:
  - 
    barycentric age = x ± y 
    
      (| z)
    
    
    
    
    
  
- 
    MSWD = x, p(χ2) = y 
    
    
    
    
  
- 
    dispersion = x ± y 
    
    
    
    
  
Aitchison, J., 1982, The statistical analysis of compositional data.
Journal of the Royal Statistical Society, v. 44, p. 139-177.
Aitchison, J., 1986, The statistical analysis of compositional
data.  London, Chapman and Hall, 416 p.
Vermeesch, P., 2008. Three new ways to calculate average (U-Th)/He
ages.
Chemical Geology, 249(3), pp.339-347.
Vermeesch, P., 2010. HelioPlot, and the treatment of overdispersed
(U-Th-Sm)/He data. Chemical Geology, 271(3), pp.108-111.