Perhaps you should try some spelling variations:
dan hanh » dang hanh, dan khanh, dan thanh
mang dai » mang dat, mang dau, mang lai
thuc dan » thuc hanh, hoc dan, thuc vat
lang dai » lang hai, lang mai, lang chai
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ve cam » ve cham, ve cac, ve cai
va cam » va cham, va cac, va cao
vi hoa » voi hoa, vi hoc, va hoa

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

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((mang dai) OR (lang dai)) hoi. hieu ((ve cam) OR (va cam)) thuc dan hanh vi hoa viet~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ((mang dai) OR (lang dai)) hoi. hieu ((ve cam) or (va cam)) thuc dan hanh vi hoa viet~".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((mang dai) OR (lang dai)) hoi. hieu ((ve cam) or (va cam)) thuc dan hanh vi hoa viet*.