Walker   | first = George P.L.   | coauthors =   Edgardo Cañón-Tapia, & Emilio Herrero-Bervera
  | title = Origin of vesicle layering and double imbrication by endogenous growth in the Birkett basalt flow �Columbia river plateau   | journal = Journal of Volcanology and Geothermal Research     | volume = 88  | issue =   | pages = 15–28  | publisher =   | date = 1999  | url =   | jstor =    | issn =   | doi =   | id =   | accessdate = 28 August 2011 }} 
{{Cite journal  | last =