Thanks Russ, so lets say a sentence in between [1] and [2] contained source [3] that means I need to reference like this:
A neuron is a special type of cell that is found in the bodies of most animals (all members of the group Eumetazoa, to be precise—this excludes only sponges and a few other very simple animals). [1] The features that define a neuron are electrical excitability and the presence of synapses, which are complex membrane junctions used to transmit signals to other cells. [2][3] The body's neurons, plus the glial cells that give them structural and metabolic support, together constitute the nervous system. In vertebrates, the majority of neurons belong to the central nervous system, but some reside in peripheral ganglia, and many sensory neurons are situated in sensory organs such as the retina and cochlea.[2]
Which implies from the start to [1] contains info from source 1 only, from [1] to [2][3] contains info from [2] and [3] only and finally from [2][3] to [2] contains info from source [2] only.