Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
nang ma » tang ma, sang ma, nang cao
sach tu » sach thu, cach tu, sach ty
lang xa » lang ha, dang xay, lang van
thuc va » thuc vat, thuc day
dan vi » doan vi, don vi, dan va
vi cua » vai cua, di 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 tu ((lang xa) or (nang ma)) hoi. hieu van nam ((thuc va) OR (thuc dan)) dan vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach tu ((lang xa) OR (nang ma)) hoi. hieu van nam ((thuc va) OR (thuc dan)) dan vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach tu ((lang xa) or (nang ma)) hoi. hieu van nam ((thuc va) OR (thuc dan)) dan vi cua viet".
• Adding a wildcard symbol may retrieve word variants: thu sach tu ((lang xa) or (nang ma)) hoi. hieu van nam ((thuc va) OR (thuc dan)) dan vi cua viet*.