diff --git a/rtengine/helperavx.h b/rtengine/helperavx.h
index eb32277c3..528760a92 100644
--- a/rtengine/helperavx.h
+++ b/rtengine/helperavx.h
@@ -1,3 +1,9 @@
+////////////////////////////////////////////////////////////////
+//
+//  this code was taken from http://shibatch.sourceforge.net/
+//  Many thanks to the author: Naoki Shibata
+//
+////////////////////////////////////////////////////////////////
 #ifndef __AVX__
 #error Please specify -mavx.
 #endif
diff --git a/rtengine/helpersse2.h b/rtengine/helpersse2.h
index 0f1fc5759..23dd016fa 100644
--- a/rtengine/helpersse2.h
+++ b/rtengine/helpersse2.h
@@ -1,3 +1,12 @@
+////////////////////////////////////////////////////////////////
+//
+//  this code was taken from http://shibatch.sourceforge.net/
+//  Many thanks to the author of original version: Naoki Shibata
+//
+//  This version contains modifications made by Ingo Weyrich
+//
+////////////////////////////////////////////////////////////////
+
 #ifndef __SSE2__
 #error Please specify -msse2.
 #endif
diff --git a/rtengine/sleef.c b/rtengine/sleef.c
index 2377aea79..bc38a3cfb 100644
--- a/rtengine/sleef.c
+++ b/rtengine/sleef.c
@@ -1,3 +1,12 @@
+////////////////////////////////////////////////////////////////
+//
+//  this code was taken from http://shibatch.sourceforge.net/
+//  Many thanks to the author of original version: Naoki Shibata
+//
+//  This version contains modifications made by Ingo Weyrich
+//
+////////////////////////////////////////////////////////////////
+
 #ifndef _SLEEFC_
 #define _SLEEFC_
 
diff --git a/rtengine/sleef.h b/rtengine/sleef.h
deleted file mode 100644
index 101a4faff..000000000
--- a/rtengine/sleef.h
+++ /dev/null
@@ -1,51 +0,0 @@
-typedef struct {
-    double x, y;
-} double2;
-
-typedef struct {
-    float x, y;
-} float2;
-
-double xsin(double d);
-double xcos(double d);
-double2 xsincos(double d);
-double xtan(double d);
-double xasin(double s);
-double xacos(double s);
-double xatan(double s);
-double xatan2(double y, double x);
-double xlog(double d);
-double xexp(double d);
-double xpow(double x, double y);
-
-double xsinh(double x);
-double xcosh(double x);
-double xtanh(double x);
-double xasinh(double x);
-double xacosh(double x);
-double xatanh(double x);
-double xldexp(double x, int q);
-int xilogb(double d);
-
-double xfma(double x, double y, double z);
-double xsqrt(double d);
-double xcbrt(double d);
-
-double xexp2(double a);
-double xexp10(double a);
-double xexpm1(double a);
-double xlog10(double a);
-double xlog1p(double a);
-
-float xsinf(float d);
-float xcosf(float d);
-float2 xsincosf(float d);
-float xtanf(float d);
-float xasinf(float s);
-float xacosf(float s);
-float xatanf(float s);
-float xatan2f(float y, float x);
-float xlogf(float d);
-float xexpf(float d);
-float xpowf(float x, float y);
-float xcbrtf(float d);
diff --git a/rtengine/sleefsseavx.c b/rtengine/sleefsseavx.c
index 1b0c9a0ae..a55fcf897 100644
--- a/rtengine/sleefsseavx.c
+++ b/rtengine/sleefsseavx.c
@@ -1,3 +1,13 @@
+////////////////////////////////////////////////////////////////
+//
+//  this code was taken from http://shibatch.sourceforge.net/
+//  Many thanks to the author of original version: Naoki Shibata
+//
+//  This version contains modifications made by Ingo Weyrich
+//
+////////////////////////////////////////////////////////////////
+
+
 #ifndef SLEEFSSEAVX
 #define SLEEFSSEAVX