Perhaps you should try some spelling variations:
dau tien » van tien
dau tren » dat tren, dau tieng, dau trong
cam truc » cau truc, nam truc, lam truoc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
dao cao » dao tao, bao cao, tao cao
cu tren » tu tren, dua tren
truc va » thuc va, thuc vat, trung va
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
ve cam » ve cham, ve cac, va cam
ma hoi » mai hoi, xa hoi, ma hoa
va dao » ca 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 ma hoi. hieu ve cam truc va dao cao ((((dau tren) or (dau tien))) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. hieu ve cam truc va dao cao ((((dau tren) OR (dau tien))) OR (cu tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. hieu ve cam truc va dao cao ((((dau tren) or (dau tien))) or (cu tren))*.