Perhaps you should try some spelling variations:
hoach tren » hoach trong, hoach toan, hoc tren
cach khoan » cac khoan, cach hoan, bach khoa
tren thuc » trien thuc, tron thuc, trinh thuc
thuc cach » thuoc sach, truoc cach, thuc hanh
sach tai » sach bai, sach tham, sach dao
tai thuc » thai thuc, tri thuc, dai thuc
thuc anh » thuc hanh, thuy anh, thu anh
anh khoa » doanh khoa, hang khoa
khoan le » khoan ke, hon le, khoan va
le trong » le trung, ly trong, le tang
tu sach » thu sach, su sach, te sach
khoa he » hoa he, khoa hoc, khong he

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu sach tai thuc anh khoa he thong ) or ( thu hoach tren thuc cach khoan le trong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach tai thuc anh khoa he thong ) OR ( thu hoach tren thuc cach khoan le trong )).
• Adding a wildcard symbol may retrieve word variants: (( tu sach tai thuc anh khoa he thong ) or ( thu hoach tren thuc cach khoan le trong ))*.