Complex sentence: Research in 1940 by DVL's K.A. Kawalki lead to subsonic profiles very similar to the supercrtical profiles, therefore the objection in the year 1984 against the US-patent specification for the supercritical airfoil.
Split into simpler sentences: Research in 1940 by DVL's K.A. Kawalki, leading to subsonic profils very similar to the supercrtical profils. Therefore objection in the year 1984 against the US-patent specification for the supercritical airfoil.