Mplus小白，错误ERROR in MODEL command Unknown variable(s) in a BY statemen：X11

语法为：
DATA:
  FILE IS C:\Users\jifa\Desktop\原始数据与分析结果\Final_data.dat;
VARIABLE:
  NAMES ARE ID X11 X12 X14 X15 X16 X21 X22 X23 X24 X31 X32 X33 X34
  Y12 Y13 Y14 Y15 Y16 Y21 Y22 Y23 Y24 Y25 Y26 Z1 Z2 Z3 Z4 Z5 Z6
  X1 X2 X3 Y1 Y2 Z;
  USEVAR are Y12-Y26;
ANALYSIS:
  ESTIMATOR IS ML;
  BOOTSTRAP ARE 10000;
  CONVERGENCE IS 0.1;

MODEL:
  !MEASUREMENT MODEL

  X1 BY X11-X16;
  X2 BY X21-X24;
  X3 BY X31-X34;

  Y1 BY Y12-Y16;
  Y2 BY Y21-Y26;
  Z BY Z1-Z6;



  !STRUCTURAL MODEL
  Y1 ON X1 X2 X3;
  Y2 ON X1 X2 X3;
  Z ON X1 X2 X3 Y1 Y2;


  MODEL INDIRECT:
  Z IND X1;
  Z IND X2;
  Z IND X3;


OUTPUT:
  SAMPSTAT STDYX CINTERVAL(BCBOOTSTRAP);