Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dinh dat » dinh ket, dinh van, dinh lam
thi van » thi lan, thi hanh, thi nang
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
nang ma » tang ma, sang ma, nang cao
dat cua » dai cua, day cua, mat cua
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
tuc va » truc va, tuc xa, duc va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky nang ma hoi. ((thien van) or (thi van)) cham ((tuc va) OR (thuc va)) dinh dat cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ma hoi. ((thien van) OR (thi van)) cham ((tuc va) OR (thuc va)) dinh dat cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ma hoi. ((thien van) or (thi van)) cham ((tuc va) OR (thuc va)) dinh dat cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ma hoi. ((thien van) or (thi van)) cham ((tuc va) OR (thuc va)) dinh dat cua tre*.