Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
thuc day » thuc dan, thuc vat
hoc viet » hoc hien
hieu he » hieu ve, hieu le, hieu hien
hiem he » hiem xe, thien he, hiem cho
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan
may hoi » may thoi, tay hoi, mai hoi
ky mang » ky nang, ke mang, ky dang
danh vi » hanh vi, dinh vi, danh di
vi hoc » li hoc, va hoc

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 mang may hoi. ((hieu he) OR (hiem he)) nam ((thuc va) or (thuc day)) danh vi hoc viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky mang may hoi. ((hieu he) OR (hiem he)) nam ((thuc va) OR (thuc day)) danh vi hoc viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky mang may hoi. ((hieu he) OR (hiem he)) nam ((thuc va) or (thuc day)) danh vi hoc viet".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky mang may hoi. ((hieu he) OR (hiem he)) nam ((thuc va) or (thuc day)) danh vi hoc viet*.