if (document.images) {
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  students_r3_c1_f1 = new Image(143 ,36); students_r3_c1_f1.src = "students/images/students_r3_c1.gif";
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  students_r4_c1_f1 = new Image(143 ,36); students_r4_c1_f1.src = "students/images/students_r4_c1.gif";
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  students_r7_c1_f1 = new Image(143 ,38); students_r7_c1_f1.src = "students/images/students_r7_c1.gif";
  }