Complex sentence: N. Berkovits, A. Sen and B. Zwiebach, "Tachyon condensation in superstring field theory", Nucl. Phys. B 587 (2000) 147 The only known analytic solutions to the classical equations of motion are marginal deformations.
Split into simpler sentences: N. Berkovits, A. Sen and B. Zwiebach, "Tachyon condensation in superstring field theory", Nucl.Phys. B587 (2000) 147 The only known analytic solutions to the classical equations of motion are marginal deformations.