Perhaps you should try some spelling variations:
may thoi » gay thoi, tay thoi, may thong
thuc van » thuc dan, thuc va, thuc hanh
su sach » so sach, vu sach
may thi » day thi, mai thi, may tai
hieu ve » hieu va, hieu van
y mang » cay mang
ve cam » ve cham, ve cac, va cam
anh vi » hanh vi, anh va, anh ve
vi hoa » voi hoa, vi hoc, va hoa

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach y mang ((may thoi) OR (may thi)). hieu ve cam ((thuc van) or (thuc vat)) anh vi hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y mang ((may thoi) OR (may thi)). hieu ve cam ((thuc van) OR (thuc vat)) anh vi hoa viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y mang ((may thoi) OR (may thi)). hieu ve cam ((thuc van) or (thuc vat)) anh vi hoa viet".
• Adding a wildcard symbol may retrieve word variants: su sach y mang ((may thoi) OR (may thi)). hieu ve cam ((thuc van) or (thuc vat)) anh vi hoa viet*.