anchor.diff:              (subscriptionAddress, unsubscribe, world)
           { ObserverAddress = observation.ObserverAddress; Subscribe = subscribe }
   
  -    /// Subscribe an observation, handling each event with the given 'handleEvent' procedure,
  +    /// Subscribe to an observation, handling each event with the given 'handleEvent' procedure,
       /// returning both an unsubscription procedure as well as the world as augmented with said
       /// subscription.
       let subscribeWithUnsub handleEvent observation world =
  
positive.code:         let observation = { ObserverAddress = observation.ObserverAddress; Subscribe = subscribe }
          observation.Subscribe world |> _bc
  
      /// Subscribe an observation, handling each event with the given 'handleEvent' procedure.
      let subscribe handleEvent observation world =
          subscribeWithUnsub handleEvent observation world |> snd
  
  
negative.code:             (subscriptionAddress, unsubscribe, world)
          { ObserverAddress = observation.ObserverAddress; Subscribe = subscribe }
  
      /// Terminate an observation when the observer is removed from the world.
      let lifetime (observation : Observation<'a, 'o>) : Observation<'a, 'o> =
          until (RemovingEventAddress ->>- observation.ObserverAddress) observation
  
      /// Subscribe to an observation until the observer is removed from the world,
      /// returning both an unsubscription procedure as well as the world as augmented with said
      /// subscription.
      let monitorWithUnsub eventAddress observation world =
          (observation |> lifetime |> subscribeWithUnsub eventAddress) world
  
      /// Subscribe to an observation until the observer is removed from the world.
      let monitor eventAddress observation world =
          monitorWithUnsub eventAddress observation world |> snd
      
  