diff --git a/README.md b/README.md
index 64a1625..1ee9331 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,8 @@
 # apple1
 use build.sh to compile
+
+documentation extracted from:
+http://e-tradition.net/bytes/6502/6502_instruction_set.html
+http://www.llx.com/~nparker/a2/opcodes.html
+
+check them out for a comprehensive documentation.