Perhaps you should try some spelling variations:
trinh han » trinh quan
thu hang » thi hang, thuc hanh, thu huong
phat duc » pham duc, phan duc, phan duoc
va trinh » van trinh, va tinh, lap trinh
tu sach » thu sach, su sach, te sach
tu hang » tu hanh, tu hung, ty hang
hieu va » lieu va, hieu qua
han cua » hang cua, nhan cua, than cua
cua tre » cua te, cuu tre, cua triet

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 ((tu hang) or (thu hang)) xa hoi. hieu va phat duc va trinh han cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((tu hang) OR (thu hang)) xa hoi. hieu va phat duc va trinh han cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ((tu hang) or (thu hang)) xa hoi. hieu va phat duc va trinh han cua tre*.