Digital flash cards including links to digital content

A computer program product including one or more non-transitory machine-readable mediums encoded with instructions that when executed by one or more processors cause a process to be carried out for controlling access to flash cards, the process comprising:

• accessing, via a user interface, a flash card mode wherein previously created first one or more flash cards and second one or more flash cards are accessible via the flash card mode and while in the flash card mode causing simultaneous display of (i) a first option to access the first one or more flash cards that are accessible without authorization to access digital content that includes answers to one or more questions displayed on the first one or more flash cards, and (ii) a second option to access the second one or more flash cards that are pre-viewable, but not fully accessible, without authorization to access the digital content,
• the digital content being stored separately from the first and second one or more flash cards;
• in response to a selection of the second option, causing display of a flash card of the second one or more flash cards, the displayed flash card including at least a first virtual side and a second virtual side, the first virtual side displaying a question, wherein an answer to the question is included in the digital content that is stored separately from the first and second one or more flash cards;
• in response to user access to the digital content not being authorized, causing display of, on the second virtual side of the displayed flash card, a canonical fragment identifier (CFI) that identifies a portion of the digital content with the answer to the question and an option to gain access to the digital content that includes the answer identified by the CFI, and in response to the option to gain access being selected from the second virtual side of the displayed flash card, authorizing user access to at least the portion of the digital content that includes the answer to the question.

A computer program product including one or more non-transitory machine-readable mediums encoded with instructions that when executed by one or more processors cause a process to be carried out for controlling access to flash cards, the process comprising:

• accessing, via a user interface, a flash card mode, and while in the flash card mode, in response to user input including selecting a portion of digital content and performing a create command, create a flash card having at least two virtual sides, the portion of digital content having a location within the digital content;
• cause simultaneous display of (1) a canonical fragment identifier (CFI) that identifies the location of the selected portion of digital content and (2) a prompt that prompts the user to enter a question related to the selected portion of digital content, the canonical fragment identifier being visually associated with a first virtual side of the flash card, and the question being visually associated with a second virtual side of the flash card and in response to user access to the digital content not being authorized, causing display of, on the first virtual side of the displayed flash card, the canonical fragment identifier that identifies the portion of the digital content with the answer to the question and an option to gain access to the digital content that includes the answer identified by the canonical fragment identifier.