Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
tam thuc » tham thuc, am thuc, nam thuc
nang mai » nang ma, nang tai, lang mai
cua tre » cuu tre, cua triet, dua tren
dinh du » dinh duc, dinh cu, dinh tu
va dinh » van dinh, va kinh, va tinh
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
thi van » thi lan, thi hanh, thi nang
mai hoi » mai khoi, dai hoi, lai hoi
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: hoc sach ky nang mai hoi. ((thien van) or (thi van)) tam thuc va dinh du ((cua tre) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky nang mai hoi. ((thien van) OR (thi van)) tam thuc va dinh du ((cua tre) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: hoc sach ky nang mai hoi. ((thien van) or (thi van)) tam thuc va dinh du ((cua tre) or (cua te))*.