diff --git a/doc/terminology.org b/doc/terminology.org
index 8e17fa0..6218d89 100644
--- a/doc/terminology.org
+++ b/doc/terminology.org
@@ -9,9 +9,6 @@ GameBoy terminology.
 
 *** Hardware
 
-https://gbdev.io/pandocs/Specifications.html
-https://gbdev.io/pandocs/Memory_Map.html
-
 | Name            | Modern equivalent | Description                               |
 |-----------------+-------------------+-------------------------------------------|
 | APU             |                   | Audio Processing Unit                     |
@@ -22,7 +19,7 @@ https://gbdev.io/pandocs/Memory_Map.html
 
 *** Opcode
 
-| Name      | Bits | Sign     | Mnemonics |    1 |   2 |    3 |   4 | Description                  | Note              |
+| Name      | Bits | Sign     | Mnemonics |    [[https://gbdev.io/gb-opcodes/optables/][1]] |   [[https://rgbds.gbdev.io/docs/v0.5.2/gbz80.7/][2]] |  [[https://gekkio.fi/files/gb-docs/gbctr.pdf][3]]/[[http://marc.rawer.de/Gameboy/Docs/GBCPUman.pdf][3]] |   [[https://gbdev.io/pandocs/CPU_Instruction_Set.html][4]] | Description                  | Note              |
 |-----------+------+----------+-----------+------+-----+------+-----+------------------------------+-------------------|
 |           |      |          |           |  <r> | <r> |  <r> | <r> |                              |                   |
 | immediate |    8 | unsigned |           |   d8 |  n8 |    n |     | Next byte in memory          |                   |
@@ -35,12 +32,17 @@ https://gbdev.io/pandocs/Memory_Map.html
 | immediate |    8 | unsigned |           | (a8) | n16 |  (n) |   n | 0xff00 + next byte in memory | write to I/O-port |
 | condition |      |          |           |   NZ |  cc |      |   f | Execute if condition met     |                   |
 
-d = data
+d = data \\
 n = constant
 
 *** Variables
 
 | Name   | Meaning            |
 |--------+--------------------|
-| size   | amount of bytes    |
 | length | amount of elements |
+| size   | amount of bytes    |
+
+** References
+
+- https://gbdev.io/pandocs/Memory_Map.html
+- https://gbdev.io/pandocs/Specifications.html