Identifying Potential Determinants of Faecal Contamination on Domestic Floors in Three Settings in Rural Kenya: A Mixed Methods Analysis by Legge, H, Kazungo, K, Muli, S, Elson, L, Mwongeli, J, Halliday, KE, Ochwal, V, Oswald, W, Dreibelbis, R, Njomo, D, Mwandawiro, C, Fillinger, U, Pullan, R, Kepha, S