Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
te sach » toc sach
hanh va » hang va, hanh vi
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
hieu vu » hieu ve, hieu su, dieu vu
mai hoi » mai khoi, dai hoi, lai hoi
xac va » tac va, ac va, bac va
va cua » va chua, via cua, ca cua
cua te » cua tu

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 mai hoi. ((hieu vu) OR (hieu va)) kham ((xac va) or (duc va)) hanh va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky nang mai hoi. ((hieu vu) OR (hieu va)) kham ((xac va) OR (duc va)) hanh va cua te*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky nang mai hoi. ((hieu vu) OR (hieu va)) kham ((xac va) or (duc va)) hanh va cua te*".