Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
nhan thuc » nhan luc, dan thuc, toan thuc
danh kien » dinh kien, danh viet, linh kien
doc sach » hoc sach, toc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
kien cua » khien cua, dien cua, tien cua
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
va danh » va dinh, va dan, va hanh
cua tre » cua te, cuu tre, cua triet
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: doc sach ky nang ma hoi. hieu van ((tham thuc) or (nhan thuc)) va danh kien cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ky nang ma hoi. hieu van ((tham thuc) OR (nhan thuc)) va danh kien cua tre.
• Adding a wildcard symbol may retrieve word variants: doc sach ky nang ma hoi. hieu van ((tham thuc) or (nhan thuc)) va danh kien cua tre*.