Perhaps you should try some spelling variations:
thuoc sach » hoc sach, thuat sach, thuoc sinh
nuoc sach » nguoi sach, hoc sach, cuoc cach
van hanh » van thanh, ban hanh, van anh
hanh va » hang va, hanh vi
hieu va » lieu va, hieu qua
hieu ve » hieu van
cua tre » cua te, cuu tre, cua triet
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
cac bo » bac bo, cac co
bo van » vo van, so van, do van
va cua » va chua, via cua, ca cua

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

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