source: Bone marrow is the flexible tissue found in the hollow interior of bones.
target: Bone marrow is a flexible tissue.  It is found in the hollow inside part of bones.
references: Bone marrow is a flexible tissue.  It is found in the hollow inside part of bones. Bone narrow is the flexible substances thatcan be found in the empty space inside the bones. Bone marrow is found in the inside of bones. The flexible tissue found inside bones is bone marrow. Bone marrow is the movable thing in the inside of bones. Bone marrow is the flexible tissue found in bones. Bone marrow is the flexible tissue found in the hollow inside of bones. Bone marrow is the moveable tissue found in the empty insides of bones. Bone marrow is the flexible tissue found inside bones Bone marrow is tissue found in the middle of bones.