One model of these substances consists of two independent phases, one condensed state and one normal state, and was formulated by Tizsa. The mixing of a working liquid and one of these substances allows cooling down to 2 millikelvins in a dilution refrigerator. One of these substances can be created using (-5[1])isentropic compression (10[1])in a (10[1])Pomeranchuk (10[1])cell. (10[1]-5[1])These substances display quantized (10[2])vortices (-5[1])called (-5[1])rotons (-5[1])that can form (10[3]-5[1])in these substances (-5[2])as predicted (-5[1])by Landau. (10[2]-5[4])These substances (10[1]-5[2])have high (10[1])thermal conductivity (10[2])due to propagating temperature waves called (-5[1])second sound. (10[3])Below the lambda (10[1])point, (-5[2])helium-4 (10[2]-5[1])transitions (10[3]-5[2])to one (10[1])of these (10[1])substances. (10[5]-5[3])These (-5[1])substances (10[1]-5[1])can form Rollin (10[1])films (-5[1])that enable them (10[1])to creep (10[1])up (10[1])walls. (10[1]-5[2])For 10 points, (10[1])name these substances that have zero viscosity (10[2]-5[1])and flow without friction. (10[1])■END■ (10[22]0[2])