Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cam thuc » am thuc, nam thuc, cam thu
manh hai » minh hai, thanh hai, van hai
lanh hai » thanh hai, lang chai, lanh dao
thuc dan » thuc hanh, hoc dan, thuc vat
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
sach ly » sach y, sach lo, sach ty
ly nang » ky nang, ly hang, ly vang
van cam » van nam, van lam, van cau
ma hoi » mai hoi, ma hoa, me hoi

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 nang ((ma hoi) or (xa hoi)). hieu van cam thuc dan ((lanh hai) OR (manh hai)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ly nang ((ma hoi) OR (xa hoi)). hieu van cam thuc dan ((lanh hai) OR (manh hai)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ly nang ((ma hoi) or (xa hoi)). hieu van cam thuc dan ((lanh hai) OR (manh hai)) cau tren".
• Adding a wildcard symbol may retrieve word variants: su sach ly nang ((ma hoi) or (xa hoi)). hieu van cam thuc dan ((lanh hai) OR (manh hai)) cau tren*.