Perhaps you should try some spelling variations:
hoc truc » hoc thuc, hoc trung, hoc thuoc
co trach » bo trach, co tranh, co tich
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
dang xa » dang xay, lang xa, dang ha
va hanh » van hanh, va thanh, va danh
ky dang » ky nang, ky danh
dao suu » da suu
dao huu » do huu
te sach » toc sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky dang xa hoi. hieu va ((hoc truc) or (co trach)) va hanh ((dao suu) OR (dao huu)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky dang xa hoi. hieu va ((hoc truc) OR (co trach)) va hanh ((dao suu) OR (dao huu)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky dang xa hoi. hieu va ((hoc truc) or (co trach)) va hanh ((dao suu) OR (dao huu)) viet".
• Adding a wildcard symbol may retrieve word variants: te sach ky dang xa hoi. hieu va ((hoc truc) or (co trach)) va hanh ((dao suu) OR (dao huu)) viet*.