Authors: J William Schopf; Anatoliy B Kudryavtsev; Malcolm R Walter; Martin J Van Kranendonk; Kenneth H Williford; Reinhard Kozdon; John W Valley; Victor A Gallardo; Carola Espinoza; David T Flannery Journal: Proc Natl Acad Sci U S A Date: 2015-02-02 Impact factor: 11.205