diff --git a/src/ComplexElliptic.jl b/src/ComplexElliptic.jl
index 32b8747..a9d242a 100644
--- a/src/ComplexElliptic.jl
+++ b/src/ComplexElliptic.jl
@@ -8,7 +8,68 @@ Year: 2023
 """
 
 
-using SpecialFunctions, Elliptic
+using SpecialFunctions
+
+function ellipkkp(L)
+    # Complete elliptic integral of the first kind, with complement.
+    if L > 10
+        K = π / 2
+        Kp = π * L + log(4)
+        return K, Kp
+    end
+
+    m = exp(-2 * π * L)
+    a0 = 1.0
+    b0 = sqrt(1 - m)
+    s0 = m
+    i1 = 0
+    mm = 1.0
+    while mm > eps()
+        a1 = (a0 + b0) / 2
+        b1 = sqrt(a0 * b0)
+        c1 = (a0 - b0) / 2
+        i1 += 1
+        w1 = 2^i1 * c1^2
+        mm = maximum(w1)
+        s0 += w1
+        a0 = a1
+        b0 = b1
+    end
+    K = π / (2 * a1)
+
+    if m == 1
+        K = Inf
+    end
+
+    if nargout() > 1
+        a0 = 1.0
+        b0 = sqrt(m)
+        a1=0
+        s0 = 1 - m
+        i1 = 0
+        mm = 1.0
+        while mm > eps()
+            a1 = (a0 + b0) / 2
+            b1 = sqrt(a0 * b0)
+            c1 = (a0 - b0) / 2
+            i1 += 1
+            w1 = 2^i1 * c1^2
+            mm = maximum(w1)
+            s0 += w1
+            a0 = a1
+            b0 = b1
+        end
+        Kp = π / (2 * a1)
+        if m == 0
+            Kp = Inf
+        end
+    else
+        Kp = nothing
+    end
+
+    return K, Kp
+end
+
 
 function polyval(p::Vector{T}, x::T) where T <: Real
     result = zero(T)