Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
hieu van » hieu va, thien van, lieu va
cham duc » cham soc, pham duy, phan duc
xanh tai » hanh tai, anh tai, vanh tai
va trien » va truyen, va thiet, va tuyen
tu sach » thu sach, su sach, te sach
va xanh » va danh, va hanh, va anh
tai va » thai va, mai va, tri va
x hoi » xa hoi, o hoi, x ho

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 thu nang x hoi. hieu van ((cham duc) or (pham duc)) va xanh tai va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu nang x hoi. hieu van ((cham duc) OR (pham duc)) va xanh tai va trien.
• Adding a wildcard symbol may retrieve word variants: tu sach thu nang x hoi. hieu van ((cham duc) or (pham duc)) va xanh tai va trien*.