diff --git a/code/lattice.f90 b/code/lattice.f90
index 09069501d..9705e788a 100644
--- a/code/lattice.f90
+++ b/code/lattice.f90
@@ -1037,8 +1037,10 @@ subroutine lattice_initializeStructure(myPhase,CoverA)
          sn(1:3,i) = lattice_bcc_systemSlip(4:6,i)
          sdU = sd(1:3,i) / math_norm3(sd(1:3,i))
          snU = sn(1:3,i) / math_norm3(sn(1:3,i))
+         ! "np" and "nn" according to Gröger_etal2008, Acta Materialia 56 (2008) 5412–5425, table 1 (corresponds to their "n1" for positive and negative slip direction respectively)
          np = math_mul33x3(math_axisAngleToR(sdU,60.0_pReal*INRAD), snU)
          nn = math_mul33x3(math_axisAngleToR(-sdU,60.0_pReal*INRAD), snU)
+         ! Schmid matrices with non-Schmid contributions according to Koester_etal2012, Acta Materialia 60 (2012) 3894–3901, eq. (17) ("n1" is replaced by either "np" or "nn" according to either positive or negative slip direction)
          sns(1:3,1:3,1,1,i) = math_tensorproduct(sdU, np)
          sns(1:3,1:3,2,1,i) = math_tensorproduct(-sdU, nn)
          sns(1:3,1:3,1,2,i) = math_tensorproduct(math_vectorproduct(snU, sdU), snU)