Perhaps you should try some spelling variations:
trinh tai » trinh toan, trinh tu, trinh han
hieu van » hieu va, thien van, lieu va
tinh tai » tinh thai, tinh hai, hinh tai
dang mau » dong mau, dang van, dang su
van cac » van hac, van cau, van bac
luc may » truc may, phuc may
cac luc » cau luc, coc luc, cac nuoc
tu sach » thu sach, su sach, te sach
mau hoi » cau hoi, mai hoi, mau ho
ky dang » ky nang, ky danh
vu sach » vu bach, su sach, vu khach
cuc tre » duc tre, cua tre, cuu tre

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) or (vu sach)) ky dang mau hoi. hieu van cac luc may ((tinh tai) OR (trinh tai)) cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (vu sach)) ky dang mau hoi. hieu van cac luc may ((tinh tai) OR (trinh tai)) cuc tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (vu sach)) ky dang mau hoi. hieu van cac luc may ((tinh tai) OR (trinh tai)) cuc tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (vu sach)) ky dang mau hoi. hieu van cac luc may ((tinh tai) OR (trinh tai)) cuc tre*.