Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cau thuc » cau truc, cuu thuc, can thuc
vat danh » va danh, van danh, luat danh
ky lang » ky nang, ky dang, ky tang
ky danh » ky anh, ky dang
van cau » van dau, van hau, van chat
vai cua » dai cua, hai cua, lai cua
doi cua » dai cua, hoi cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((ky lang) or (ky danh)) xa hoi. hieu van cau thuc vat danh ((vai cua) or (doi cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky lang) OR (ky danh)) xa hoi. hieu van cau thuc vat danh ((vai cua) OR (doi cua)) tre.
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky lang) or (ky danh)) xa hoi. hieu van cau thuc vat danh ((vai cua) or (doi cua)) tre*.