  Consider a communication scenario over a noiseless channel where a sender is
required to broadcast messages to multiple receivers, each having side
information about some messages. In this scenario, the sender can leverage the
receivers' side information during the encoding of messages in order to reduce
the required transmissions. This type of encoding is called index coding. In
this paper, we study index coding with two cooperative senders, each with some
subset of messages, and multiple receivers, each requesting one unique message.
The index coding in this setup is called two-sender unicast index coding
(TSUIC). The main aim of TSUIC is to minimize the total number of transmissions
required by the two senders. Based on graph-theoretic approaches, we prove that
TSUIC is equivalent to single-sender unicast index coding (SSUIC) for some
special cases. Moreover, we extend the existing schemes for SSUIC, viz., the
cycle-cover scheme, the clique-cover scheme, and the local-chromatic scheme to
the corresponding schemes for TSUIC.
