return {
    ['stone-furnace']=true,
    ['steel-furnace']=true,
    ['electric-furnace']=true,
    ['assembling-machine-1']=true,
    ['assembling-machine-2']=true,
    ['assembling-machine-3']=true,
    ['beacon']=true,
    ['centrifuge']=true,
    ['chemical-plant']=true,
    ['oil-refinery']=true,
    ['storage-tank']=true,
    ['nuclear-reactor']=true,
    ['steam-engine']=true,
    ['steam-turbine']=true,
    ['boiler']=true,
    ['heat-exchanger']=true,
    ['stone-wall']=true,
    ['gate']=true,
    ['gun-turret']=true,
    ['laser-turret']=true,
    ['flamethrower-turret']=true,
    ['radar']=true,
    ['lab']=true,
    ['big-electric-pole']=true,
    ['substation']=true,
    ['rocket-silo']=true,
    ['pumpjack']=true,
    ['electric-mining-drill']=true,
    ['roboport']=true
}