Reduced linear fractional representation of nonlinear systems for stability analysis ⁎ ⁎The research was partially supported by the grant K115694 of the National Research, Development and Innovation Office - NKFIH. The project has also been supported by the European Union, co-financed by the European Social Fund through the grant EFOP-3.6.3-VEKOP-16-2017-00002. The research leading to the results presented in the paper was supported (also) by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences.