Perhaps you should try some spelling variations:
sach truc » cach thuc, sach tren, sach thu
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
cuu tre » cua tre, cau tren, cau treo
danh di » danh du, xanh di, danh dien
va danh » va dinh, va dan, va hanh
truc va » thuc va, thuc vat, trung va
va sach » van sach, va cach, a sach
hieu va » lieu va, hieu qua
cu tren » tu tren, dua tren
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, 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: vu sach ky nang ((o hoi) OR (o hoc)). hieu va sach truc va danh di ((cuu tre) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang ((o hoi) OR (o hoc)). hieu va sach truc va danh di ((cuu tre) OR (cu tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang ((o hoi) OR (o hoc)). hieu va sach truc va danh di ((cuu tre) or (cu tren))*".