Information retrieval systems and methods are disclosed for presenting items of interest to a user of a computer-based data repository, where the items are presented in the form of lists generated by other users. In the lubricating structure, the crank room and a transmission room are divided by a partition, an oil storage room communicating with a discharging portion of the scavenging pump is formed, and an oil passage for lubricating a transmission is formed in the transmission shaft along the shaft center and is opened to the oil storage room. The moving assembly includes a sliding module and at least one rotating module. The main frame includes an inner wall surface having a first rib extending peripherally and projecting inwardly into the space in the main frame. Also disclosed are method and apparatus for mounting a flexible printing plate.