diff --git a/cbits/dpi.c b/cbits/dpi.c
index d1b07bb6..eb31fe6e 100644
--- a/cbits/dpi.c
+++ b/cbits/dpi.c
@@ -1,3 +1,10 @@
+/*
+Based on code from notnullnotvoid's comment on:
+https://seabird.handmade.network/blogs/p/2460-be_aware_of_high_dpi
+
+Author's page: https://handmade.network/m/notnullnotvoid
+*/
+
 #if !defined(_WIN32)
 
 void initDpiAwareness() {
diff --git a/cbits/glew.c b/cbits/glew.c
index a1ad77da..96fe0dc7 100644
--- a/cbits/glew.c
+++ b/cbits/glew.c
@@ -1,3 +1,5 @@
+// Based on code from cocreature's https://github.com/cocreature/nanovg-hs
+
 #include <GL/glew.h>
 #include <stdio.h>
 
diff --git a/src/Monomer/Graphics/FFI.chs b/src/Monomer/Graphics/FFI.chs
index f90390ce..334e4260 100644
--- a/src/Monomer/Graphics/FFI.chs
+++ b/src/Monomer/Graphics/FFI.chs
@@ -1,6 +1,7 @@
 {-|
 Module      : Monomer.Graphics.FFI
-Copyright   : (c) 2018 Francisco Vallarino
+Copyright   : (c) 2018 Francisco Vallarino,
+              (c) 2016 Moritz Kiefer
 License     : BSD-3-Clause (see the LICENSE file)
 Maintainer  : fjvallarino@gmail.com
 Stability   : experimental