Who did what?

Would anybody be able to tell us who did what among Jo Mankiewicz and Sidney Lumet in this film, two directors I love.
Both their names are credited as directors but I don't think they directed anything as this film is made of archival footage, might they have been in charge of the direction of those famous "celebrity bridges" nobody seems to care about and which seem to be of no interest? I'm not at all sure about this last possibility.
Did they take the editing in charge at any level? Well... 2 supervising editors are credited for this, so...
Thanks for any help about this...