Perhaps you should try some spelling variations:
tu tieng » luc tieng, tu tuong, tu trong
dua tren » dung tren
truc van » thuc van, truc ban, truc dan
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
truc va » thuc va, thuc vat, trung va
nang ma » tang ma, sang ma, nang cao
tu sach » thu sach, su sach, te sach
va dau » va dao
ma hoi » mai hoi, xa hoi, ma hoa

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 ma hoi. hieu va dau ((truc van) OR (truc va)) hanh vi ((dua tren) or (tu tieng))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. hieu va dau ((truc van) OR (truc va)) hanh vi ((dua tren) OR (tu tieng)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ma hoi. hieu va dau ((truc van) OR (truc va)) hanh vi ((dua tren) or (tu tieng))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. hieu va dau ((truc van) OR (truc va)) hanh vi ((dua tren) or (tu tieng))*.