Textbook codes used in the analysis.
| National curriculum | Publisher | Code |
|---|---|---|
| 1st | Ministry of Education | 1a [44] |
| 2nd | Ministry of Education | 2a [45] |
| 3rd | Ministry of Education | 3a [46] |
| 4th | Ministry of Education | 4a [47] |
| 5th | Ministry of Education | 5a [48] |
| 6th | Ministry of Education | 6a [49] |
| 7th | Ministry of Education | 7a [50] |
| 2007 revised | Ministry of Education | 07a [51] |
| 2009 revised | Ministry of Education | 09a [52] |
| 2015 revised | Ministry of Education | 15a [53] |
| 2015 revised | Donga | 15b [54] |
| 2015 revised | Chunjae(Lee) | 15c [55] |
| 2015 revised | Jihak | 15d [56] |
| 2015 revised | Chunjae(Shin) | 15e [57] |
| 2015 revised | Miraen | 15f [58] |
| 2015 revised | Visang | 15g [59] |
| 2015 revised | Kumsung | 15h [60] |
| 2015 revised | I-scream | 15i [61] |
| 2015 revised | Gimmyoung | 15j [62] |