Negotiable Instruments Law
Section 3. When promise is unconditional.-An unqualified order or promise to pay is unconditional within the meaning of this Act, though coupled with-
(a) An indication of a particular fund out of which reimbursement is to be made, or a particular account to be debited with the amount; or
(b) A statement of the transaction which gives rise to the instrument.
But an order or promise to pay out of a particular fund is not unconditional.