Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
su sach » so sach, vu sach
hanh ve » hanh vi, hanh va, hanh kem
su viet » so viet
y tang » ky tang, 6 tang, 7 tang
ve cau » ke cau, ve cac, le cau
va cau » van cau, va cac, va dau
ve su » va su

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