Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
phan lai » phan loai, phan lap, phan lan
thu sach » thuat sach, thuoc sach, thu hoach
nang hoi » nang noi, nang hoc, nang ho
va phan » van phan, va phat, va phap
truc va » thuc va, thuc vat, trung va
hieu va » lieu va, hieu qua
tu sach » su sach, te sach, tu cach
hoi hoi » hoi hoc, hoc hoi, hoi doi
ty nang » ky nang, ty xang, ty hang
hieu su » hieu sau, tieu su, hieu so

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