Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
dinh dau » dinh dat, dinh du, danh dau
cham tuc » nham thuc, pham thuc, tham thuc
dau cua » dai cua, day cua, cau cua
va dinh » van dinh, va kinh, va tinh
cua tre » cua te, cuu tre, cua triet
thi van » thi lan, thi hanh, thi nang
nang xa » nang x, lang xa, nang ma
tuc va » thuc va, truc va, tuc xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) ky nang xa hoi. ((thien van) or (thi van)) cham tuc va dinh dau cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky nang xa hoi. ((thien van) OR (thi van)) cham tuc va dinh dau cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) ky nang xa hoi. ((thien van) or (thi van)) cham tuc va dinh dau cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) ky nang xa hoi. ((thien van) or (thi van)) cham tuc va dinh dau cua tre*.