Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
vai cua » dai cua, hai cua, lai cua
dau vai » dau va, dau hai, dau tai
hieu va » lieu va, hieu qua
sang ma » tang ma, nang ma, sang tao
hieu ve » hieu van
ky sang » ky nang, ky dang, ky tang
ma hoi » mai hoi, xa hoi, ma hoa
tuc va » thuc va, truc va, duc va
cua te » cua tu

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 sang ma hoi. ((hieu ve) or (hieu va)) cac ((tuc va) OR (tuc xa)) dau vai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky sang ma hoi. ((hieu ve) OR (hieu va)) cac ((tuc va) OR (tuc xa)) dau vai cua te*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky sang ma hoi. ((hieu ve) or (hieu va)) cac ((tuc va) OR (tuc xa)) dau vai cua te*".