Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nam truc » nam truoc, nam thuc, nam trung
truc van » truc va, thuc van, truc ban
van hanh » van thanh, ban hanh, van anh
cau tren » dau tren, ca tren, cau treo
sach ky » sac ky, sach ty, sach kem
cao hoi » cau hoi, co hoi, cao hoc
cu tren » tu tren, dua tren

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach ky) OR (sach y)) nang cao hoi. hieu van nam truc van hanh vi ((cau tren) or (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ky) OR (sach y)) nang cao hoi. hieu van nam truc van hanh vi ((cau tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ky) OR (sach y)) nang cao hoi. hieu van nam truc van hanh vi ((cau tren) or (cu tren))".
• Adding a wildcard symbol may retrieve word variants: so ((sach ky) OR (sach y)) nang cao hoi. hieu van nam truc van hanh vi ((cau tren) or (cu tren))*.