1. ASTM, 1999, “Standard guide for using the gravity method for subsurface investigation,” D 6430‐99, ASTM International, West Conshohocken, PA.
2. Butler, Dwain K., 1980, “Microgravimetric techniques for geotechnical applications,” MP GL‐80‐13, US Army Engineer Research and Development Center, Vicksburg, MS.
3. Butler, Dwain K., 1983, “Microgravimetry and the theory, measurement and application of gravity gradients,” PhD Dissertation, Texas A&M University, College Station, TX.
4. Interval gravity‐gradient determination concepts
5. Microgravimetric and gravity gradient techniques for detection of subsurface cavities