Perhaps you should try some spelling variations:
nang cau » nang cao, hang cau, nang dau
hieu van » hieu va, thien van, lieu va
thuc cac » thuc cach, phuc cac, thac cac
cau tren » dau tren, ca tren, cau treo
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
tuc cac » tu cac, tich cac
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: tu sach ky nang cau hoi. hieu van nam ((thuc cac) or (tuc cac)) dan ca ((cau tren) OR (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang cau hoi. hieu van nam ((thuc cac) OR (tuc cac)) dan ca ((cau tren) OR (cu tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang cau hoi. hieu van nam ((thuc cac) or (tuc cac)) dan ca ((cau tren) OR (cu tren))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang cau hoi. hieu van nam ((thuc cac) or (tuc cac)) dan ca ((cau tren) OR (cu tren))*.