no diagram but referenced in text

[sdevriese]

http://gpg.geosci.xyz/content/seismic/seismic_refraction_irregular_layers.html

Second paragraph says "consider diagram to the right" but there is no diagram... @lheagy @thast @dccowan

[sdevriese]

Also, the end of this page just ends... without describing the travel times for hagedoorn's method