Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
hanh tai » thanh tai, hang tai, han tai
cau tren » cu tren, dau tren, ca tren
mai khoi » mai khoa, tai khoa, cac khoi
lang mai » lang dai, lang hai, lang man
hieu ve » hieu va, hieu van
ve tham » va tham, ve cham, vi tham
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
ky lang » ky nang, ky dang, ky tang
cuu tre » cua tre, cau treo
tu sach » thu sach, su sach, te sach

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 lang mai khoi. hieu ve tham thuc va hanh tai ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang mai khoi. hieu ve tham thuc va hanh tai ((cuu tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang mai khoi. hieu ve tham thuc va hanh tai ((cuu tre) or (cau tren))*.