diff --git a/examples/webgl_materials_bumpmap.html b/examples/webgl_materials_bumpmap.html
index 1bb46518e537e775d365ce4e05a5aec0f8ed3596..d99d2ffb5801ee5dab891be3be3455a2d72facd0 100644
--- a/examples/webgl_materials_bumpmap.html
+++ b/examples/webgl_materials_bumpmap.html
@@ -39,7 +39,7 @@
diff --git a/examples/webgl_materials_bumpmap_skin.html b/examples/webgl_materials_bumpmap_skin.html
index 2adbabc835076216934134b9c168d3bccd887935..fc7f49e52187bbe4ab6f9c53a0d63d9b540947c6 100644
--- a/examples/webgl_materials_bumpmap_skin.html
+++ b/examples/webgl_materials_bumpmap_skin.html
@@ -36,7 +36,7 @@
diff --git a/src/renderers/shaders/ShaderChunk/bumpmap_pars_fragment.glsl b/src/renderers/shaders/ShaderChunk/bumpmap_pars_fragment.glsl
index a3b5add02be2119020fc49f5f24947b254eff120..b120bd8cb3ea4b143eacc5b0c89c67115ba6eaf2 100644
--- a/src/renderers/shaders/ShaderChunk/bumpmap_pars_fragment.glsl
+++ b/src/renderers/shaders/ShaderChunk/bumpmap_pars_fragment.glsl
@@ -3,8 +3,8 @@
uniform sampler2D bumpMap;
uniform float bumpScale;
- // Derivative maps - bump mapping unparametrized surfaces by Morten Mikkelsen
- // http://mmikkelsen3d.blogspot.sk/2011/07/derivative-maps.html
+ // Bump Mapping Unparametrized Surfaces on the GPU by Morten S. Mikkelsen
+ // http://api.unrealengine.com/attachments/Engine/Rendering/LightingAndShadows/BumpMappingWithoutTangentSpace/mm_sfgrad_bump.pdf
// Evaluate the derivative of the height w.r.t. screen-space using forward differencing (listing 2)