Perhaps you should try some spelling variations:
duc tien » duc thien, luc tieng, thuc tien
tinh tai » trinh tai, tinh thai, tinh hai
cam tuc » cam xuc, cam tu, nam thuc
duc tre » duoc tren
va tinh » may tinh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
mau hoi » mai hoi, mau ho, mau hop
ky dang » ky nang, ky danh
tuc va » thuc va, truc va, tuc xa
ve cam » ve cham, ve cac, va cam

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 dang ((mau hoi) or (cau hoi)). hieu ve cam tuc va tinh tai ((duc tre) or (duc tien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((mau hoi) OR (cau hoi)). hieu ve cam tuc va tinh tai ((duc tre) OR (duc tien)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((mau hoi) or (cau hoi)). hieu ve cam tuc va tinh tai ((duc tre) or (duc tien))*.