Reference | Informal | Public formal | Private formal | Formal (not categorized) |
---|
 | 48 | 7 | 38 | N/A |
[7] | 47 | N/A | N/A | 53 |
 | 57 | N/A | N/A | 43 |
[37] | 33 | 30 | 9 | N/A |
[28] | 47 | N/A | N/A | 26 |
[26] | 77 | N/A | N/A | N/A |
[27] | 67 | N/A | N/A | 38 |
[34] | 12 | 74 | 15 | 33 |
[35] | 38 | 32 | 24 | N/A |
[44] | 65 | N/A | N/A | N/A |
[25] | 86 | 9 | 6 | 25 |
[29] | 85 | 17 | N/A | N/A |