Perhaps you should try some spelling variations:
hoc truc » hoc thuc, hoc trung, hoc thuoc
co trach » bo trach, co tranh, co tich
hanh dao » lanh dao, thanh dat, thanh dam
sau viet » su viet, dau viet, sau biet
te sach » toc sach
ky dang » ky danh
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
dao sau » tao sau, day sau, dao cau

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