Form factors of the nucleon have been extracted from experiment with high
precision. However, lattice calculations have failed so far to reproduce the
observed dependence of form factors on the momentum transfer. We have embarked
on a program to thoroughly investigate systematic effects in lattice
calculation of the required three-point correlation functions. Here we focus on
the possible contamination from higher excited states and present a method
which is designed to suppress them. Its effectiveness is tested for several
baryonic matrix elements, different lattice sizes and pion masses.Comment: 7 pages, 8 figure
