Perhaps you should try some spelling variations:
trinh doc » trinh do, trinh hoa, trinh co
tinh doi » trinh do, tinh hoc, tinh son
cu tren » tu tren, dua tren
cam duc » cam xuc, cao duc, pham duc
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va
san ky » sang ky, van ky, dan ky
ma hoi » mai hoi, xa hoi, ma hoa
tu san » thu san, tu ban, tu can

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu san ky nang ma hoi. ((hieu va) OR (hieu qua)) cam duc va ((tinh doi) OR (trinh doc)) cu tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu san ky nang ma hoi. ((hieu va) OR (hieu qua)) cam duc va ((tinh doi) or (trinh doc)) cu tren~".
• Adding a wildcard symbol may retrieve word variants: tu san ky nang ma hoi. ((hieu va) OR (hieu qua)) cam duc va ((tinh doi) or (trinh doc)) cu tren*.