Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hanh vai » hanh vi, hanh va, hanh tai
dan hanh » dang hanh, dan khanh, dan thanh
thuc dan » thuc hanh, hoc dan, thuc vat
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
hoa hoi » khoa hoi, hoa hoc, hoc hoi
hoa doi » hoa dai, hoc doi, xoa doi
ky lang » ky nang, ky dang, ky tang
ve nam » he nam, va nam, te nam
le nam » ly nam, he nam, le na
vai su » va su, van su, lai su

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 lang ((hoa hoi) OR (hoa doi)). hieu ((ve nam) or (le nam)) thuc dan hanh vai su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang ((hoa hoi) OR (hoa doi)). hieu ((ve nam) OR (le nam)) thuc dan hanh vai su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang ((hoa hoi) OR (hoa doi)). hieu ((ve nam) or (le nam)) thuc dan hanh vai su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ((hoa hoi) OR (hoa doi)). hieu ((ve nam) or (le nam)) thuc dan hanh vai su triet*.