Perhaps you should try some spelling variations:
tham thuc » nham thuc, tam thuc, thai thuc
sach tham » sach nha
pham thuc » phap thuc, pham chuc, nham thuc
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
lang ha » long ha
cua tre » cua te, cuu tre, cua triet
ha hoi » hoa hoi, ha noi, xa hoi
va cua » va chua, via cua, ca cua

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 ty) or (sach tham)) lang ha hoi. hieu va ((tham thuc) or (pham thuc)) va hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (sach tham)) lang ha hoi. hieu va ((tham thuc) OR (pham thuc)) va hanh va cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) or (sach tham)) lang ha hoi. hieu va ((tham thuc) or (pham thuc)) va hanh va cua tre*.