docs: function(df1, df2) {
           return {
              d: function(x, logp) { return df(df1, df2, logp)(x); },
              p: function(q, lowerTail, logp) {
                 return pf(df1, df2, lowerTail, logp)(q);
              },
              q: function(p, lowerTail, logp) {
                 return qf(df1, df2, lowerTail, logp)(p);
              },
              r: function() { return rf(df1, df2)(); }
           };
        }