Perhaps you should try some spelling variations:
tinh oai » tinh hai, tinh bai, tinh lai
su triet » su viet, su tien, ve triet
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
va tinh » may tinh
cac tu » cac thu, cach tu, cac du
oai su » loai su, lai su, oi su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang ma) or (van xay)) hoi. hieu va cac tu va tinh oai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang ma) OR (van xay)) hoi. hieu va cac tu va tinh oai su triet.
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang ma) or (van xay)) hoi. hieu va cac tu va tinh oai su triet*.