We take formula 75 as a clopen subbase for our topology on formula 106. There are many ways that the subbase or base can be weakened. The theorem is a quick corollary of the Alexander subbase theorem. Good maintenance practices center on keeping water out of the pavement, subbase and subsoil. At first the airfield was used as subbase of Hamilton Field. It can be mixed into new pavement or used as a subbase or fill material. The pavement and subbase thicknesses are designed to withstand the wheel loads. To topologize "O" we will specify a subbase for its topology. A second subbase is formed by taking the subfamily where and are rational. Sometimes, geogrids are used to reinforce the subbase and further strengthen the roads. The material is crushed to provide subbase for roads and driveways, among other purposes. If there is a subbase course, the base course is constructed directly about this layer. This leads to excess moisture in the shoulders and subbase at the road edge. Then the collection of all such is a subbase for the compact-open topology on . In other words, the sets {"p"("U")} form a subbase for the topology on "X".