Perhaps you should try some spelling variations:
dang khai » dang khoi, dang hai, quang khai
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
khai cau » khai cac, phan cau, hai chau
cau thuc » cau truc, cuu thuc, can thuc
nang ma » tang ma, sang ma, nang cao
ly nang » ky nang, ly hang, ly vang
van cau » van dau, van hau, van chat
thuc va » thuc vat, thuc dan, thuc day
va dang » van dang, va nang, va lang
vu sach » vu bach, vu khach
su sach » so sach
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) or (vu sach)) ly nang ma hoi. hieu van cau thuc va dang khai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) ly nang ma hoi. hieu van cau thuc va dang khai cau tren.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) ly nang ma hoi. hieu van cau thuc va dang khai cau tren*.