fix typo in comment (closes #438)

src/beta_inc.jl

@@ -899,9 +899,8 @@ function _beta_inc(a::T, b::T, x::T, y::T) where {T<:Union{Float16, Float32}}
 end
 
 
-#GW Cran, KJ Martin, GE Thomas, Remark AS R19 and Algorithm AS 109: A Remark on Algorithms AS 63: The Incomplete Beta Integral and AS 64: Inverse of the Incomplete Beta Integeral,
-#Applied Statistics,
-#Volume 26, Number 1, 1977, pages 111-114.
+#GW Cran, KJ Martin, GE Thomas, Remark AS R19 and Algorithm AS 109: A Remark on Algorithms: AS 63: The Incomplete Beta Integral AS 64: Inverse of the Incomplete Beta Function Ratio,
+#Applied Statistics, Volume 26, Number 1, 1977, pages 111-114.  https://doi.org/10.2307/2346887
 
 """
     beta_inc_inv(a, b, p, q=1-p)