Bar chart. Data table with 3 rows and 7 columns follows.
| ScienceDirect | ProQuestDissertation&Thesis | Academic Search Complete | SpringerLink | ABI/Inform | IEL | |
|---|---|---|---|---|---|---|
| ปี 2017 | 199,994 | 27,682 | 353,268 | 40,988 | 40,976 | 134,820 |
| ปี 2018 | 173,237 | 21,605 | 70,487 | 45,133 | 21,634 | 175,829 |