Perhaps you should try some spelling variations:
trinh toan » tinh toan, thanh toan, trinh han
trinh tai » trinh tu, trinh han, chinh tai
tang van » dang van, hoang van, trong van
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
xuc va » duc va, tuc va, luc va
va cam » va cham, va cac, va cao

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 ty ((tang van) or (lang xa)) hoi. hieu va cam xuc va ((trinh tai) OR (trinh toan)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((tang van) OR (lang xa)) hoi. hieu va cam xuc va ((trinh tai) OR (trinh toan)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ((tang van) or (lang xa)) hoi. hieu va cam xuc va ((trinh tai) OR (trinh toan)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((tang van) or (lang xa)) hoi. hieu va cam xuc va ((trinh tai) OR (trinh toan)) cua tre*.