Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
thu nhap » thu ha, khu nha
thu nam » tu nam, thu nhat, thu ngan
lai cua » dai cua, hai cua, lai chau
dan lai » dan loai, dan lap, dan lat
hieu he » hieu ve, hiem he, hieu le
sach ky » sach y, sach ty, sach kem
mai hoi » mai khoi, dai hoi, lai hoi
cua tre » cua te, cuu tre, cua triet
he nam » ha nam, nghe nam
sac ky » cac ky, sai ky

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 ky) or (sac ky)) nang mai hoi. hieu he nam ((thu nam) OR (thu nhap)) dan lai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang mai hoi. hieu he nam ((thu nam) OR (thu nhap)) dan lai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) nang mai hoi. hieu he nam ((thu nam) OR (thu nhap)) dan lai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang mai hoi. hieu he nam ((thu nam) OR (thu nhap)) dan lai cua tre*.