Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hoc thuc » hoc huu
va dinh » van dinh, va kinh, va tinh
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
vi cuu » vinh cuu
vi luu » vi lua
va hoc » van hoc
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ky nang ((o hoi) OR (o hai)). hieu va hoc thuc va dinh ((vi cuu) or (vi luu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((o hoi) OR (o hai)). hieu va hoc thuc va dinh ((vi cuu) OR (vi luu)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ((o hoi) OR (o hai)). hieu va hoc thuc va dinh ((vi cuu) or (vi luu)) tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((o hoi) OR (o hai)). hieu va hoc thuc va dinh ((vi cuu) or (vi luu)) tre*.