Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
voi hoat » toi hoat, doi hoat, vo hoat
cach tu » cach thuc
voi hoa » voi khoa, boi hoa, voi ho
va dong » van dong, ha dong, xa dong
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
mai hoi » mai khoi, dai hoi, lai hoi
cac tu » cac thu, cac du, tac tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky nang mai hoi. hieu va ((cac tu) OR (cach tu)) va dong ((voi hoa) or (voi hoat)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang mai hoi. hieu va ((cac tu) OR (cach tu)) va dong ((voi hoa) OR (voi hoat)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang mai hoi. hieu va ((cac tu) OR (cach tu)) va dong ((voi hoa) or (voi hoat)) viet".
• Adding a wildcard symbol may retrieve word variants: vu sach ky nang mai hoi. hieu va ((cac tu) OR (cach tu)) va dong ((voi hoa) or (voi hoat)) viet*.