References: Following sites contain useful information related to CPT, SPT, Vs, liquefaction, seismic settlement, and so on:

1. Dr. Peter K. Robertson
2. CPT’10: 2nd International Symposium on Cone Penetration Testing
3. CPT’14: 3rd International Symposium on Cone Penetration Testing 
4. Professor Paul Mayne at Georgia Tech.
5. Professors Idriss, I.M. and Boulanger, R. W. at UC Davis
6. Professor Jonathan P. Stewart at UCLA
7. Professor Ronald D. Andrus (Vs related paper Andrus & Stokoe (2000))
8. FHWA – Geotechnical Engineering – General Publications
9. vulcanhammer.net — the page with Geotechnical and Marine Engineering Resources

CPT Providers: Companies that provide Cone Penetration Testing in southern California:

1. Middle Earth Geo Testing Inc.
2. Gregg Drilling & Testing, Inc. (Gregg)
3. Fugro Consultants
4. Kehoe Testing & Engineering, Inc. (KTE)