Perhaps you should try some spelling variations:
chet duoc » che duoc, cho duoc, che quoc
van hanh » van thanh, ban hanh, van anh
dang hoa » dang hoai, dang khoa, dong hoa
cua tre » cua te, cuu tre, cua triet
va chet » va chiet, va che, va chat
va hanh » va thanh, va danh, ban hanh
hieu va » lieu va, hieu qua
ky dang » ky nang, ky danh
su xac » pu xac, su cac
vi cua » vai cua, di cua
su sac » su sach, su cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sac) or (su xac)) ky dang hoa hoc. hieu va chet duoc ((va hanh) OR (van hanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sac) OR (su xac)) ky dang hoa hoc. hieu va chet duoc ((va hanh) OR (van hanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sac) or (su xac)) ky dang hoa hoc. hieu va chet duoc ((va hanh) OR (van hanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sac) or (su xac)) ky dang hoa hoc. hieu va chet duoc ((va hanh) OR (van hanh)) vi cua tre*.