Perhaps you should try some spelling variations:
quoc quan » qua quan, luc quan, hoc quan
lang chai » lang ha, lang cua, lang phi
hieu van » hieu va, thien van, lieu va
lanh dai » lanh dao, lanh hai, lang dai
tu sach » thu sach, su sach, te sach
cua tre » cua te, cuu tre, cua triet
duc van » duc va, duc tan, duc manh
sach ky » sac ky, sach y, sach ty
van lam » van nam
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang

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 ky lang xa hoi. hieu van lam ((quoc quan) or (duc van)) ((lanh dai) or (lang chai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang xa hoi. hieu van lam ((quoc quan) OR (duc van)) ((lanh dai) OR (lang chai)) cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang xa hoi. hieu van lam ((quoc quan) or (duc van)) ((lanh dai) or (lang chai)) cua tre*.