Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hanh tai » thanh tai, hang tai, han tai
hanh vai » hanh vi, hanh va, hanh van
thuc ban » thuoc ban, thuc dan, thu ban
ca viet » va viet, co viet, hoa viet
va tham » van tham, va cham, va thanh
hieu va » lieu va, hieu qua
lai hoi » dai hoi, lai hoa, lai roi
mai hoi » mai khoi, dai hoi, mai doi
ky mang » ky nang, ke mang, ky dang
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky mang ((mai hoi) OR (lai hoi)). hieu va tham thuc ban ((hanh vai) or (hanh tai)) ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky mang ((mai hoi) OR (lai hoi)). hieu va tham thuc ban ((hanh vai) OR (hanh tai)) ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky mang ((mai hoi) OR (lai hoi)). hieu va tham thuc ban ((hanh vai) or (hanh tai)) ca viet".
• Adding a wildcard symbol may retrieve word variants: tu sac ky mang ((mai hoi) OR (lai hoi)). hieu va tham thuc ban ((hanh vai) or (hanh tai)) ca viet*.