Solution : https://service.sap.com/sap/support/notes/152971 (SAP Service marketplace login required)
Key words : 
customizing ' ' documentation ' ' special texts-menue special imports -> import, customizing ' ' documentation ' ' special texts-select, ~ftp/general/r3server/language/note, separate directory-call transaction smlt, = delete lines            detail default 'n', directory n_nl including file nnltx, language dutch including language supplementation, button schedule import-maintain, select report    technical names, dsyat-spras default 'n'
Related Notes : 
       
| 440484 | |
| 158404 | Latest note on language import 4.0B / SR1 | 
| 97583 | Current note about language import 4.0B |