Use at your own risk.
BACK UP YOUR FILES FIRST. THIS WILL ERASE EVERYTHING AND YOU WILL LOSE ROOT!!!!!
1. Download files from the links in the attached text file.
2. Download ODIN. I used 3.04.
3. Put phone in download mode by holding vol. down + home + power and then hit volume up to continue
4. Select the appropriate files to flash (look at the attached s4a_odin.jpg file)
5. Hit start and wait. The first reboot will take a while.
Check the text file for the link. I537UCUBML2 (includes all files).7z contains everything you need except for ODIN. The individual files are also available in that folder just in case you need a specific one.
New links are up as of 01/27/14!
BL_I537UCUBML2_2244695_REV06_user_low_ship_MULTI_C ERT.tar: AC906659B3D1E5818A96D3FF3424EA99
CP_I537UCUBML2_2244695_REV06_user_low_ship_MULTI_C ERT.tar: BBCC7DA1B1DAD7C5C93033E7CC6BC286
CSC_ATT_I537ATTBML2_2244695_REV06_user_low_ship_MU LTI_CERT.tar: 4EEA95BD6901FDBA8A9FE58F261D8412
AP_I537UCUBML2_2244695_REV06_user_low_ship_MULTI_C ERT.tar: 07B2A316FB92C488FF953F8009794F7F