Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cac luc » cau luc, coc luc, cac nuoc
cu tren » tu tren, dua tren
luc va » duc va, tuc va, loc va
va don » va dong, va doc, va do

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang x ho. hieu va cac luc va don vi ((cu tren) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x ho. hieu va cac luc va don vi ((cu tren) OR (dau tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x ho. hieu va cac luc va don vi ((cu tren) or (dau tren))*.