9. An electronic device, comprising: one or more processors; a display; a touch sensor to detect user inputs of varying force; a memory coupled to the one or more processors, the memory storing a content item and instructions that are executable by the one or more processors to perform acts comprising: in response to detecting a first user input using the touch sensor, selecting a first entry from supplemental content to output to the display, the first entry selected based at least in part on the first user input; in response to detecting, using the touch sensor, a second user input having an amount of force greater than a predetermined threshold, selecting a second entry from the supplemental content to output to the display by prompting a user to select one of multiple different reference work entries, the second entry selected based at least in part on the amount of force of the second user input.
9. An electronic device, comprising: one or more processors; a display; a touch sensor to detect user inputs of varying force; a memory coupled to the one or more processors, the memory storing a content item and instructions that are executable by the one or more processors to perform acts comprising: in response to detecting a first user input using the touch sensor, selecting a first entry from supplemental content to output to the display, the first entry selected based at least in part on the first user input; in response to detecting, using the touch sensor, a second user input having an amount of force greater than a predetermined threshold, selecting a second entry from the supplemental content to output to the display by prompting a user to select one of multiple different reference work entries, the second entry selected based at least in part on the amount of force of the second user input. 14. An electronic device as recited in claim 9 , wherein the electronic device comprises an electronic book reader device, a handheld tablet computing device, a desktop computer, a laptop computer, or a kiosk.