Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
cau tren » cu tren, dau tren, ca tren
thuoc va » thuc va, thuoc ma, thuong va
hieu van » hieu va, thien van, lieu va
hanh ve » hanh vi, hanh va, hanh kem
va hanh » van hanh, va thanh, va danh
tu sach » thu sach, su sach, te sach
ty nang » ky nang, ty xang, ly nang
ty hang » ly hang, ty xang, thi hang
ve cau » ke cau, va cau, ve cac
x hoi » o hoi, x ho, 5 hoi

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 nang) OR (ty hang)) ((x hoi) or (xa hoi)). hieu van nam thuoc va hanh ve cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty nang) OR (ty hang)) ((x hoi) OR (xa hoi)). hieu van nam thuoc va hanh ve cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ty nang) OR (ty hang)) ((x hoi) or (xa hoi)). hieu van nam thuoc va hanh ve cau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty nang) OR (ty hang)) ((x hoi) or (xa hoi)). hieu van nam thuoc va hanh ve cau tren*.