Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
thuc day » thuc dan, thuc vat
hanh hai » thanh hai, nhanh hai, hang hai
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
van cau » van dau, van hau, van chat
truc va » thuc va, thuc vat, trung va
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
cuu tre » cua tre, cau treo
ma hoi » mai hoi, xa hoi, ma hoa

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 hoi. hieu van cau ((truc va) or (thuc day)) hanh hai ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ma hoi. hieu van cau ((truc va) OR (thuc day)) hanh hai ((cuu tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ma hoi. hieu van cau ((truc va) or (thuc day)) hanh hai ((cuu tre) or (cau tren))*.