Perhaps you should try some spelling variations:
hanh hai » thanh hai, nhanh hai, hang hai
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
hai cau » hai chau, hai chu, hai hau
va cam » va cham, va cac, va cao
xuc va » duc va, luc va, xac va
tuc va » thuc va, truc va, tuc xa
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: su sach ky nang ((o hoi) OR (o hoc)). hieu va cam ((xuc va) or (tuc va)) hanh hai cau tao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang ((o hoi) OR (o hoc)). hieu va cam ((xuc va) OR (tuc va)) hanh hai cau tao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang ((o hoi) OR (o hoc)). hieu va cam ((xuc va) or (tuc va)) hanh hai cau tao".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang ((o hoi) OR (o hoc)). hieu va cam ((xuc va) or (tuc va)) hanh hai cau tao*.