Perhaps you should try some spelling variations:
dau truc » cau truc, dai truc, doan truc
truc van » truc va, thuc van, truc ban
van hanh » van thanh, ban hanh, van anh
tu tieng » luc tieng, tu tuong, tu trong
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
tu tren » tu truyen, tu trong, dua tren
va dau » va dao

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 xa hoi. hieu va dau truc van hanh vi ((tu tren) or (tu tieng))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang xa hoi. hieu va dau truc van hanh vi ((tu tren) OR (tu tieng)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang xa hoi. hieu va dau truc van hanh vi ((tu tren) or (tu tieng))*.