Perhaps you should try some spelling variations:
sach ty » sach y, sach tu, sach thu
cac duc » cac du, cao duc, cac dac
tu sach » thu sach, su sach, te sach
qua cac » cua cac
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
ma hoi » mai hoi, xa hoi, ma hoa
ca dan » cac dan, ca dao
vai su » va su, lai su, tai su
van su » dan su
va dan » va dao, va dau, va dap

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 ty nang ma hoi. hieu qua cac duc ((va dan) OR (ca dan)) ((vai su) or (van su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ma hoi. hieu qua cac duc ((va dan) OR (ca dan)) ((vai su) OR (van su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ma hoi. hieu qua cac duc ((va dan) OR (ca dan)) ((vai su) or (van su)) triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ma hoi. hieu qua cac duc ((va dan) OR (ca dan)) ((vai su) or (van su)) triet*.