DCER: (Direct Current) Electrical Resistivity, aka Electrical Resistivity.
CH 12 Electrical Resistivity from LITE (Looking Into The Earth - An Introduction to Geological Geophysics by Mussett and Khan).
CH 5 Electrical Resistivity from I2AG (Introduction to Applied Geophysics by Burger, Sheehan, and Jones).
Figures from CH 5: JPGs in a ZIP file.
Electrical Properties of the Natural Environment Section 5.3 from GMEG (Geophysics for the Mineral Exploration Geoscientist).