Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hanh vai » hanh vi, hanh tai, hanh van
hanh va » hang va, hanh vi
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ((ty nang) OR (ty hang)) xa hoi. lieu va cac duc van ((hanh vai) or (hanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((ty nang) OR (ty hang)) xa hoi. lieu va cac duc van ((hanh vai) OR (hanh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((ty nang) OR (ty hang)) xa hoi. lieu va cac duc van ((hanh vai) or (hanh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: hoc sach ((ty nang) OR (ty hang)) xa hoi. lieu va cac duc van ((hanh vai) or (hanh va)) cua tre*.