Spending function overview
                        4.0: Spending function overview
Wang-Tsiatis Bounds     5.0: Wang-Tsiatis Bounds
checkScalar             6.0 Utility functions to verify variable
                        properties
gsBound                 2.6: Boundary derivation - low level
gsBoundCP               2.5: Conditional Power at Interim Boundaries
gsCP                    2.4: Conditional Power Computation
gsDesign                2.1: Design Derivation
gsDesign package overview
                        1.0 Group Sequential Design
gsProbability           2.2: Boundary Crossing Probabilities
nSurvival               3.3: Time-to-event sample size calculation
                        (Lachin-Foulkes)
normalGrid              3.1: Normal Density Grid
plot.gsDesign           2.3: Plots for group sequential designs
sfExponential           4.3: Exponential Spending Function
sfHSD                   4.1: Hwang-Shih-DeCani Spending Function
sfLDOF                  4.4: Lan-DeMets Spending function overview
sfLogistic              4.6: Two-parameter Spending Function Families
sfPoints                4.5: Pointwise Spending Function
sfPower                 4.2: Kim-DeMets (power) Spending Function
sfTDist                 4.7: t-distribution Spending Function
testBinomial            3.2: Testing, Confidence Intervals and Sample
                        Size for Comparing Two Binomial Rates
