Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
cau tren » cu tren, ca tren, cau treo
danh hai » dang hai, lanh hai, manh hai
cam truc » cau truc, nam truc, lam truoc
hieu van » hieu va, thien van, lieu va
nang ma » tang ma, sang ma, nang cao
sach ly » sach y, sach lo, sach hay
van cam » van nam, van lam, van cau
sach ty » sach y, sach tu, sach thu
truc va » thuc va, thuc vat, trung va
va danh » va dinh, va dan, va hanh
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ly) or (sach ty)) nang ma hoi. hieu van cam truc va danh hai ((cau tren) OR (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ly) OR (sach ty)) nang ma hoi. hieu van cam truc va danh hai ((cau tren) OR (dau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ly) or (sach ty)) nang ma hoi. hieu van cam truc va danh hai ((cau tren) OR (dau tren))".
• Adding a wildcard symbol may retrieve word variants: su ((sach ly) or (sach ty)) nang ma hoi. hieu van cam truc va danh hai ((cau tren) OR (dau tren))*.