Ismu, I., and E. Mikrianto. “Structure Refinement of Five Layers Aurivillius Compound: Ba4Bi2Nb2Ti3O18”. Journal of Engineering and Technological Sciences, vol. 36, no. 1, Dec. 2013, pp. 57-62, doi:10.5614/itbj.eng.sci.2004.36.1.4.