Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
vai cuu » vai cua
dan vai » dan va, dan tai, dan vat
thuc va » thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
lang ha » long ha
lang xa » dang xay, lang van
cuu tre » cua tre, cau tren, cau treo
va nam » van nam, ha nam, va nay

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 ((lang xa) OR (lang ha)) hoi. hieu va nam ((thuc va) or (thuc vat)) dan vai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky ((lang xa) OR (lang ha)) hoi. hieu va nam ((thuc va) OR (thuc vat)) dan vai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky ((lang xa) OR (lang ha)) hoi. hieu va nam ((thuc va) or (thuc vat)) dan vai cuu tre".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky ((lang xa) OR (lang ha)) hoi. hieu va nam ((thuc va) or (thuc vat)) dan vai cuu tre*.