Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, nang ma
ve cac » va cac, vien cac
lao va » tao va, cao va, bao va
vi cua » vai cua, di cua
ve ca » ve cai, ve cau, ve cua

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. hieu ((ve ca) OR (ve cac)) lao va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (doc sach)) ky nang xa hoi. hieu ((ve ca) OR (ve cac)) lao va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (doc sach)) ky nang xa hoi. hieu ((ve ca) OR (ve cac)) lao va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (doc sach)) ky nang xa hoi. hieu ((ve ca) OR (ve cac)) lao va hanh vi cua tre*.