TY - JOUR AN - 1 AU - Krishna,P.D. AU - Shankar,P.M. AU - Newhouse,V.L. TI - Subharmonic generation from ultrasonic contrast agents. JO - Phys Med Biol PY - 1999 VL - 44 SP - 681-694 M2 - 681 DO - 10.1088/0031-9155/44/3/004 ER -