1. “Mixed valent iron oxides with the 0201-1201 intergrowth structure: (Pb_1-xTl_x)Sr_4Fe_2O_9 (0≤x≤1)”. Daniel P, Barbey L, Groult D, Nguyen N, Van Tendeloo G, Raveau B, European journal of solid state and inorganic chemistry 31, 235 (1994)