Reference for Eruvin 181:9
מתקיף לה רב חסדא לשמואל ולרבי יוחנן יאמרו שני כלים בחצר אחת זה מותר וזה אסור
R'SIMEON RULED: ROOFS etc. Rab ruled: The halachah is in agreement with R'Simeon, This, however, applies only where no 'erub<span class="x" onmousemove="('comment',' By the tenants of each courtyard.');"><sup>21</sup></span> had been prepared,<span class="x" onmousemove="('comment',' For their respective courtyards. As in the absence of all 'erub they are forbidden to carry any objects from their houses into their courtyards there is no need to provide against the possibility of the carrying of an object from one of the houses into a neighbouring courtyard.');"><sup>22</sup></span> but not where one<span class="x" onmousemove="('comment',' Each courtyard for itself but no two courtyards jointly.');"><sup>23</sup></span>