| http://www.w3.org/ns/prov#value | - BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will be clear from reading the description hereafter, with reference to the accompanying figures wherein: FIGS. 1 and 2 are photographs of a foamed cement with a foam stability problem, FIG. 3 is a photograph of a stable foamed cement obtained according to the invention, FIG. 4 diagrammatically shows a method of produc
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