Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hai cua » thai cua, dai cua, hoi cua
sai cua » dai cua, lai cua, bai cua
thue va » thuc va, thuyet va, thuat va
sach ky » sac ky, sach y, sach ty
hieu he » hieu ve, hiem he, hieu le
nang ma » tang ma, sang ma, nang cao
he nam » ha nam, nghe nam
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: tu sach ky nang ma hoi. hieu he nam ((thue va) OR (thuc vat)) danh ((sai cua) or (hai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ma hoi. hieu he nam ((thue va) OR (thuc vat)) danh ((sai cua) OR (hai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ma hoi. hieu he nam ((thue va) OR (thuc vat)) danh ((sai cua) or (hai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ma hoi. hieu he nam ((thue va) OR (thuc vat)) danh ((sai cua) or (hai cua)) tre*.