Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
tan khoa » toan khoa, tran khoa, san khoa
khoa hoc » hoa hoc
gian dan » gian lang
hoi tap » hoi dap, hoc tap, hoi tai
hoc tan » hoc tang, hoc dan, hoc tap
va gian » va gianh, van gian, va giai
mo hoc » mon hoc, co hoc
hoc xa » hoc ma

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) OR (doc sach)) hoi tap, nghien cuu mo hoc tan khoa hoc xa hoi va gian dan~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (doc sach)) hoi tap, nghien cuu mo hoc tan khoa hoc xa hoi va gian dan".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (doc sach)) hoi tap, nghien cuu mo hoc tan khoa hoc xa hoi va gian dan*.