source: Bone marrow is the flexible tissue found in the hollow insides of bones
target: Bone marrow is the flexible tissue found in the hollow interior of bones.
references: Bone marrow is the flexible tissue found in the hollow interior of bones. Bone marrow is the flexible tissue found in the inner empty space of bones. Bone marrow is a mass of flexible tissue fills the interior hollow part of bones. Bone marrow is the flexible tissue found inside bones. Bone marrow is the bendable part found in the empty spot inside of bones. Bone marrow is the tissue found in the hollow interior of bones. Bone marrow is the elastic tissue found inside bones.