diff --git a/c64/day01.asm b/c64/day01.asm
index 2717b5e..d58ad25 100644
--- a/c64/day01.asm
+++ b/c64/day01.asm
@@ -7,7 +7,7 @@
 // day01
 //
 // Destroys:
-// a, x, y, $02..$04, $10..$1c, $20..$25, $fd..$fe, everything you've ever loved
+//   a, x, y, $02..$04, $10..$1c, $20..$25, $fd..$fe, everything you've ever loved
 //
 .const input_pointer  = $03
 .const buffer_pointer = $20
diff --git a/c64/math.asm b/c64/math.asm
index bf8ecaf..49d69a0 100644
--- a/c64/math.asm
+++ b/c64/math.asm
@@ -2,6 +2,8 @@
 
 *=* "Math Routines"
 
+// Multiplication routines found on
+// https://codebase64.org/doku.php?id=base:seriously_fast_multiplication
 .const T1=$03
 .const T2=$fd
 .const PRODUCT=$22