Inner and outer periods for the 2+2 quadruples. Individual proven 2+2 systems: red dots published by T. Borkovits group, black dots by our group, and the blue ones are the rest of other authors. The newly presented systems in this paper are denoted by magenta asterisk signs. The sloped dashed lines denote the period ratios 100, 1000, and 10 000, respectively. One can clearly see that the red dots have in general a shorter A-B period than our systems plotted in black.