Perhaps you should try some spelling variations:
trinh tai » trinh toan, trinh tu, trinh han
va trinh » van trinh, va tinh, lap trinh
te sach » toc sach
sach ky » sac ky, sach y, sach ty
tai cua » thai cua, tai cuc, tri cua
cac dac » cac dan, cac dai, cac bac
cac duc » cac du, cao duc, cac nuoc
hieu ve » hieu van
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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

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