Perhaps you should try some spelling variations:
sach ky » sac ky, sach y, sach ty
so cham » so kham, co cham, so chat
hieu so » thieu so
tu sach » thu sach, su sach, te sach
sang ma » tang ma, nang ma, sang tao
ky sang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
dan vi » doan vi, dan va, gan vi

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 sang ma hoi. hieu so cham ((thuc vat) or (tuc xa)) ((dan vi) OR (don vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky sang ma hoi. hieu so cham ((thuc vat) OR (tuc xa)) ((dan vi) OR (don vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky sang ma hoi. hieu so cham ((thuc vat) or (tuc xa)) ((dan vi) OR (don vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky sang ma hoi. hieu so cham ((thuc vat) or (tuc xa)) ((dan vi) OR (don vi)) cua tre*.