Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu van
hai cua » thai cua, dai cua, hoi cua
dao hai » dao thai, dai hai, do hai
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
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: thu sach ky nang ma hoa. ((hieu ve) or (hieu va)) cam ((tuc va) OR (tuc xa)) dao hai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ma hoa. ((hieu ve) OR (hieu va)) cam ((tuc va) OR (tuc xa)) dao hai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ma hoa. ((hieu ve) or (hieu va)) cam ((tuc va) OR (tuc xa)) dao hai cua te".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ma hoa. ((hieu ve) or (hieu va)) cam ((tuc va) OR (tuc xa)) dao hai cua te*.