Perhaps you should try some spelling variations:
hieu hien » bieu hien, dieu hien, chieu chien
thu sach » tu sach, thuat sach, thuoc sach
hien cac » thien cac, vien cac, hieu cac
cua viet » ca viet, hoa viet, cua vat
nang ma » tang ma, sang ma, mang may
sach ty » sach y, sach tu, sach thu
hanh di » hanh vi, hanh de, hang di
luc va » tuc va, loc va
di cua » dai cua, doi cua, de cua

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 ty ((nang ma) OR (nang cao)) hoi. hieu hien cac ((duc va) or (luc va)) hanh di cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty ((nang ma) OR (nang cao)) hoi. hieu hien cac ((duc va) OR (luc va)) hanh di cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ty ((nang ma) OR (nang cao)) hoi. hieu hien cac ((duc va) or (luc va)) hanh di cua viet".
• Adding a wildcard symbol may retrieve word variants: thu sach ty ((nang ma) OR (nang cao)) hoi. hieu hien cac ((duc va) or (luc va)) hanh di cua viet*.