Perhaps you should try some spelling variations:
hoc viet » hoc hien
may thoi » gay thoi, may thi, tay thoi
sach ky » sac ky, sach y, sach ty
thuc va » thuc dan, thuc day
bo sach » co sach, hoc sach
hieu ve » hieu va, hieu van
hieu he » hiem he, hieu le, hieu hien
ky mang » ky nang, ke mang, ky dang
dan vi » doan vi, don vi, dan va
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: bo sach ky mang may thoi. ((hieu he) OR (hieu ve)) nam ((thuc va) or (thuc vat)) dan vi hoc viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: bo sach ky mang may thoi. ((hieu he) OR (hieu ve)) nam ((thuc va) OR (thuc vat)) dan vi hoc viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "bo sach ky mang may thoi. ((hieu he) OR (hieu ve)) nam ((thuc va) or (thuc vat)) dan vi hoc viet".
• Adding a wildcard symbol may retrieve word variants: bo sach ky mang may thoi. ((hieu he) OR (hieu ve)) nam ((thuc va) or (thuc vat)) dan vi hoc viet*.