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