A basic inequality for submanifolds in a cosymplectic space form
  For submanifolds tangent to the structure vector field in cosymplectic space forms, we establish a basic inequality between the main intrinsic invariants of the submanifold, namely its sectional curvature and scalar curvature on one side; and its main extrinsic invariant, namely squared mean curvature on the other side. Some applications including inequalities between the intrinsic invariant $\delta_{M}$ and the squared mean curvature are given. The equality cases are also discussed 
Jeong-Sik Kim, Jaedong Choi