Statistics for Structural Effects in Solvolytic Reactions. 40. Carbon-13 Nuclear Magnetic Resonance Studies of Carbocations. 8. Anomalous Carbon-13 Chemical Shifts with Increasing Electron Demand in the 2-Aryl-2-norbornyl Cations and Related Systems. Evidence That These Anomalous Shifts Are Not Diagnostic for the Onset of Nonclassical σ Bridging