1. Ultraviolet observations of M1-2 (= VV 8)
2. High-speed photometry of, and speculations on, the central star of M 1-2
3. Hardorp, J., Rohlfs, K., Slettebak, A. & Stock, J. 1959, Luminous Stars in the Northern Milky Way I (Hamburg-Bergedorf: Hamburger Sternwarte and Warner and Swasey Obs.)
4. Hardorp, J., Theile, I. & Voigt, H. H. 1964, Luminous Stars in the Northern Milky Way III (Hamburg-Bergedorf: Hamburger Sternwarte and Warner and Swasey Obs.)
5. Hardorp, J., Theile, I. & Voigt, H. H. 1965, Luminous Stars in the Northern Milky Way V (Hamburg-Bergedorf: Hamburger Sternwarte and Warner and Swasey Obs.)