| http://www.w3.org/ns/prov#value | - A variation on this theme is shown in Southworth et al., U.S. Pat. No. 3,568,626, which describes reinforcing a metal foil with some other material, such as nylon, fiberglass or steel, so that the foil is not easily broken, and using shorter portions or stretchable portions so that an equipment operator will hopefully see a portion uncovered by the excavation before the pipe is damaged.
|
