1. Stata Tip 53: Where did My P-Values Go?
2. Stata Tip 97: Getting at ρ's and σ's
3. FeivesonA. H. 2005. FAQ: What is the delta method and how is it used to estimate the standard error of a transformed parameter? http://www.stata.com/support/faqs/statistics/delta-method/.
4. SribneyW., and WigginsV. 2009. FAQ: Standard errors, confidence intervals, and significance tests for ORs, HRs, IRRs, and RRRs. http://www.stata.com/support/faqs/statistics/delta-rule/.