A component of an attractor is assigned the code value '1' if the concentration of the corresponding protein is larger than 150 relative concentration units, value '0' if it is smaller than 50 relative units, and value 'X' if it is between 50 and 150 (see Methods for description of relative units for protein concentrations). All attractors except A1 preserve a single code across the considered ranges for Bcd and Cad concentrations. Attractor A1 changes its state from through to due to continuous increase of the Gt concentration for this attractor on the Bcd-Cad plane (see the existence domains for these states in Fig. 3 for the basic normalization method and Additional file 2: Figure S2 for the alternative one). All listed attractors exist in the model corresponding to the alternative normalization method, and only A1-A4 in the model associated with the basic method.