Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
sach thi » sach thu, sach tai, sach thieu
thi nang » thi cong, ki nang, thi hanh
cua viet » hoa viet, cua vat, cua dieu
dan hanh » dang hanh, dan khanh, dan thanh
thuc dan » thuc hanh, hoc dan, thuc vat
hanh ve » hanh vi, hanh va, hanh kem
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
hieu le » hieu he, hieu ly, tieu le
ca viet » va viet, co viet, hoa viet

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach thi nang x ho. ((hieu le) or (hieu ve)) nam thuc dan hanh ve ((cua viet) OR (ca viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thi nang x ho. ((hieu le) OR (hieu ve)) nam thuc dan hanh ve ((cua viet) OR (ca viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thi nang x ho. ((hieu le) or (hieu ve)) nam thuc dan hanh ve ((cua viet) OR (ca viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach thi nang x ho. ((hieu le) or (hieu ve)) nam thuc dan hanh ve ((cua viet) OR (ca viet))*.