The ISR and the 7 TeV LHC data indicate that the differential cross-section of elastic proton-proton scattering remains almost energy-independent at the transferred momentum t ≈ −0.21 GeV 2 at the level of ≈ 7.5 mb/GeV 2 . This property of dσ/dt (the "first" stationary point) appears due to the correlated growth of the total cross-section and the local slope parameter and can be expressed as a relation between the latter quantities. We anticipate that this property will be true up to 13 TeV. This enables us to normalize the preliminary TOTEM data for dσ/dt at 13 TeV and 0.05 < |t| < 3.4 GeV 2 and predict the values of dσ/dt at this energy. These data give an evidence of the second stationary point at t ≈ −2.3 GeV 2 at the level of ≈ 33 nb/GeV 2 . The energy evolution of dσ/dt looks as if the high energy elastic scattering amplitude is a sum of two similar terms. We argue that the existence of the two stationary points and the twocomponent structure of the high energy elastic scattering amplitude are general properties for all elastic processes.

We discuss a recently proposed interpretation of some model descriptions of the proton-proton elastic scattering data as a manifestation of alleged relative transparency of the central part of the interaction region in the impact parameter space. We argue that the presence of nonzero real part of the elastic scattering amplitude in the unitarity condition enables to conserve the traditional interpretation.

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