Examples of our samples. The top one is LSPM J2238+2513 obtained by KOOLS, the second from the top is LSPM J2234+2757 obtained by the Bench spectrograph, the third from the top is LSPM J0152+6021 obtained by MALLS, the fourth from the top is LSPM J0406+7916 obtained by CAFOS, and the bottom sample is LSPM J0741+6718 obtained by DIS. We note that the CCD of KOOLS had bad pixels in 6675–6715 Å, which were excluded in this study.