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