TY - RPRT TI - Reconstructing the past from imprecise knowledge of the present : some examples of non uniqueness in solving parabolic equations backward in time AU - Carasso, Alfred S PY - 2011 PB - National Institute of Standards and Technology CY - Gaithersburg, MD SN - NIST IR 7783 DO - 10.6028/NIST.IR.7783 ER -