The Hoehn’s Concordances, available as ebooks at Amazon.com, use a three-letter code for each of the sixty six books of the Bible.  That key is included in the concordances, but here it is for those who wish to print it out on their computers.  

ACT Acts 
AMS Amos 
COL Colossians 
DAN Daniel 
DEU Deuteronomy 
ECL  Ecclesiastes 
EPH Ephesians 
EST  Esther 
EXO Exodus 
EZE Ezekiel 
EZR  Ezra 
GAL Galatians 
GEN Genesis 
HAB Habakuk 
HAG Haggai 
HEB Hebrews 
HOS Hosea 
ISA Isaiah 
JAS James 
JDE Jude 
JDG Judges 
JER Jeremiah 
JHN John 
JNA Jonah 
JOB Job 
JOL  Joel 
JOS Joshua 
LAM Lamentations 
LEV  Leviticus 
LUK Luke 
MAL Malachi 
MAT Matthew 
MIC Micah 
MRK  Mark 
NAH Nahum 
NEH  Nehemiah 
NUM Numbers 
OBA Obadiah 
PHL Philippians 
PHM Philemon 
PRV  Proverbs 
PSA  Psalms 
REV Revelation 
ROM Romans 
RTH Ruth 
SNG  Song of Solomon 
TUS Titus 
ZEC Zecharaiah 
ZEP Zephaniah 
1CH  1 Chronicles 
1CO  1 Corinthians 
1JN  1 John 
1KG  1 Kings 
1PE 1 Peter 
1SA  1 Samuel  
1TH  1 Thessalonians 
1TI  1 Timothy 
2CH  2 Chronicles 
2CO  2 Corinthians 
2JN  2 John 
2KG  2 Kings 
2PE  2 Peter 
2SA  2 Samuel 
2TH  2 Thessalonians 
2TI  2 Timothy 
3JN  3 John