Perhaps you should try some spelling variations:
tinh doi » trinh doc, trinh do, tinh hoc
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
tinh di » trinh di, tinh da, tin di
nam xuc » cam xuc, nam xua, nam thuc
tang xa » trang xa, lang xa, tang ha
tang ma » mang may, tang van
cua tre » cua te, cuu tre, cua triet
xuc va » duc va, tuc va, luc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach y ((tang xa) or (tang ma)) hoi. hieu van nam xuc va ((tinh di) OR (tinh doi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((tang xa) OR (tang ma)) hoi. hieu van nam xuc va ((tinh di) OR (tinh doi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((tang xa) or (tang ma)) hoi. hieu van nam xuc va ((tinh di) OR (tinh doi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((tang xa) or (tang ma)) hoi. hieu van nam xuc va ((tinh di) OR (tinh doi)) cua tre*.