Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
dau tren » dau tien, dat tren, dau tieng
lang mai » lang dai, lang hai, lang man
hang vai » hang tai, hang hai, hang vi
hieu van » hieu va, thien van, lieu va
van pham » san pham, van phan, van phat
ca tren » cau tren, cu tren, la tren
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
ky lang » ky nang, ky dang, ky tang
thuc va » thuc vat, thuc dan, thuc day

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 hoi. hieu van pham thuc va ((hang vai) or (hang va)) ((ca tren) or (dau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang mai hoi. hieu van pham thuc va ((hang vai) OR (hang va)) ((ca tren) OR (dau tren)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang mai hoi. hieu van pham thuc va ((hang vai) or (hang va)) ((ca tren) or (dau tren))*.