Perhaps you should try some spelling variations:
tham thuc » pham thuc, tam thuc, thai thuc
danh kien » dinh kien, danh viet, linh kien
nham thuc » nhan thuc, nam thuc, nham thu
kien cua » khien cua, dien cua, tien cua
va danh » va dinh, va dan, va hanh
sach ky » sac ky, sach y, sach kem
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((sach ky) OR (sach ty)) nang xa hoi. hieu va ((tham thuc) or (nham thuc)) va danh kien cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((sach ky) OR (sach ty)) nang xa hoi. hieu va ((tham thuc) OR (nham thuc)) va danh kien cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((sach ky) OR (sach ty)) nang xa hoi. hieu va ((tham thuc) or (nham thuc)) va danh kien cua tre".
• Adding a wildcard symbol may retrieve word variants: doc ((sach ky) OR (sach ty)) nang xa hoi. hieu va ((tham thuc) or (nham thuc)) va danh kien cua tre*.