Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
cuu cong » cua cong, thu cong, cac cong
cong hoc » dong hoc, cong hoa, cong coc
dan khoa » dang khoa, da khoa, san khoa
khoa hoc » hoa hoc
van gian » van giang, dan gian, van giao
gian dan » gian lang
hoi van » hoi va, hoi dan, hai van
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 (hoc sach)) hoc tap, nghien cuu cong hoc dan khoa hoc xa hoi van gian dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) hoc tap, nghien cuu cong hoc dan khoa hoc xa hoi van gian dan.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) hoc tap, nghien cuu cong hoc dan khoa hoc xa hoi van gian dan*.