Perhaps you should try some spelling variations:
thuat tac » thuat tach, thuat tao, thuat tai
nam truoc » nam thuoc, lam truoc, nam truc
dang xay » dang van, van xay
truoc va » truc va, thuoc va, truong va
lang xa » lang ha, lang van
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
tac ky » tac ke, cac ky, tap ky
va nam » van nam, ha nam, va nay
vi hoc » li hoc, va hoc
hien » bien, vien, tien

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuat tac ky ((lang xa) or (dang xay)) hoi. hieu va nam truoc va hanh vi hoc hien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat tac ky ((lang xa) OR (dang xay)) hoi. hieu va nam truoc va hanh vi hoc hien.
• Adding a wildcard symbol may retrieve word variants: thuat tac ky ((lang xa) or (dang xay)) hoi. hieu va nam truoc va hanh vi hoc hien*.