Systems, methods, data structures, and user interfaces associated with adding, storing, and using structured data clippings with a clipbook application are described. The systems and methods can, for example, create, review and share documents, spreadsheets and presentations from any device, using any cloud storage provider. Limited relative shifting is permitted between the components of the tow bar. An additional tubular frame rail member is optionally attached to the main tubular frame rail member. The first race and the second race define a predetermined torque limit. Disclosed herein are various heterocyclic compounds and methods of using the novel anti-cancer compounds to inhibit the growth of a cancer cell, for instance a leukemia, non-small cell lung, central nervous system, skin, ovarian, renal, prostate, breast, or colon cancer cell.