The multilayer scheme and geometry of the corresponding electromagnetic boundary problem. The superstrate and substrate media are isotropic and semi-infinite. The multilayer includes spacer layers 1, 3 with thicknesses d_1,3, whose electromagnetic properties correspond to isotropic media (in particular, ENZ MMs), and the main bi-isotropic layer 2 with thickness d₂. Relative intensities I_in, I_r, I_t, ellipticities τ_in, τ_r, τ_t, polarization azimuths θ_in, θ_r, θ_t, and wave vectors k_in, k_r, k_t correspond to the incident, reflected, and transmitted waves, ψ_in and ψ_t are the angles of incidence and refraction, respectively. The fields inside of the multilayer are not shown. The inserts bounded by dotted lines illustrate orientations of the major axes of polarization ellipses of the incident, reflected and transmitted waves in the corresponding phase planes X'Y, X''Y, X'''Y, respectively. Additional notation is given in the main text.