Data sources:

6m: V band observations taken with the Russian 6-m telescope and SCORPIO spectral camera.
A7,VA,C6,C7: UBVRcRj observations by V.P.Goranskij with CCD Apogee-7p, SBIG ST-6, SBIG ST7 and PI VersArray, and SAI Crimean Station 60-cm telescope (Rc converted to Rj using formula Rj=Rc-0.5).
AA: Photoelectric observations by V.P.Goranskij, E.A.Karitskaya and A.V.Kusakin with WBVR photometer by V.G.Kornilov and 100-cm telescope of Tien-Shan Astronomical Observatory, Kazakhstan.
AAN: Photoelectric observations by V.P.Goranskij and V.G.Moshkalev with NADIR WBVR photometer and 48-cm telescope of Tien-Shan Astronomical Observatory, Kazakhstan.
AL: AAVSO Alert Notice #538, 2016.
HM: A.Henden, U.Munari, Baltic Astronomy V.17, 293, 2008.
KS: L.Kondratyeva, F.Rspaev, IBVS No.6032, 2012.
L,Do,Me: Observations by V.P.Goranskij, V.T. Doroshenko, and N.V. Metlova with the photoelectric UBV photometer by V.M.Lyuty and 60-cm telescope. SAI Crimean Station, Ukraine & Russia.
MM: V.P.Goranskij with the SAO 1-m Zeiss Telescope and the MMPP photometer polarimeter.
MR: U.Munari, G.I.Rigttti, S.Dallaporta, S.Moretti, M.Graziani, P.Valisa, Astronomer's Telegram No.8653, 2016.
MM: V.P.Goranskij with the SAO 1 m Zeiss telescope and MMPP device (Multi-Mode Photometer-Polarimeter).
pg: Photographic photometry by V.P.Goranskij, SAI Plate collection.
Pi: Photographic observations by A.I.Pihun, Odessa Plate collection.
pz: Photographic observations by R.Luthardt, IBVS No.3563, 1991 (taken from Fig.1), Sonneberg plate collection.
ShV,f79: Observations by V.P.Goranskij and E.A.Karitskaya with photoelectric UBV photometer by S.Shugarov and I.Volkov (and its BVR mode with FEU-79 (f79) photomultiplier). 70-cm telescope of SAI Moscow Observatory and 60-cm telescope of Institute of Astronomy RAS Zvenigorod Station in Moscow region.
SO: CCD UBVRc observations by E.A.Barsukova and V.P.Goranskij with EEV 42-20 and SAO 1-m Zeiss telescope (Rc converted to Rj using formula Rj=Rc-0.5).
SV: S.Yu.Shugarov with the 60 cm Zeiss G2 telescope of the Stara Lesna Observatory (Slovakia) and UBVRcIc photometer based on CCD FLI-2.
To: T.Tomov, R.Zamanov, A.Antov, L.Georgiev, IBVS 3466 (1990); T.Tomov, D.Kolev, M.Ivanov, A.Antov, et al., AsAp Suppl Vol.116, 1 (1996).
2,3,5: Other unclarified sources.