Abstract: Methods, systems and apparatus for identifying and utilizing content synchronization information are described. Methods for creating and utilizing a synchronization file that can be used to notify users when synchronization availability exists, and to identify ways to repair synchronization unavailability are described. The synchronization file includes a complete set of individual content elements that make up a content item, such as a book, where each content element has an indication whether play-back of an audio version of the content item can be synchronized with the presentation of a corresponding text version of the content item. Methods, systems and apparatus are also disclosed for providing the synchronization availability information to the user in a manner that enables the user to increase the benefits of synchronized presentation of the content item.

Abstract: Methods, systems and apparatus for identifying and utilizing content synchronization information are described. Methods for creating and utilizing a synchronization file that can be used to notify users when synchronization availability exists, and to identify ways to repair synchronization unavailability are described. The synchronization file includes a complete set of individual content elements that make up a content item, such as a book, where each content element has an indication whether play-back of an audio version of the content item can be synchronized with the presentation of a corresponding text version of the content item. Methods, systems and apparatus are al'so disclosed for providing the synchronization availability information to the user in a manner that enables the user to increase the benefits of synchronized presentation of the content item.

Abstract: Methods, systems and apparatus for identifying and utilizing content synchronization information are described. Methods for creating and utilizing a synchronization file that can be used to notify users when synchronization availability exists, and to identify ways to repair synchronization unavailability are described. The synchronization file includes a complete set of individual content elements that make up a content item, such as a book, where each content element has an indication whether play-back of an audio version of the content item can be synchronized with the presentation of a corresponding text version of the content item. Methods, systems and apparatus are also disclosed for providing the synchronization availability information to the user in a manner that enables the user to increase the benefits of synchronized presentation of the content item.

Abstract: Systems and methods are disclosed enabling recommendations of content items based on a difficulty of the content item as well as a skill level of the user. Skill-based content recommendations may be utilized, for example, in recommending content to language learners. Skill-based recommendations may be based on a variety of difficulty metrics of the content item, such as vocabulary and complexity of the language (e.g., words per paragraph, syllables per word, etc.), as well as a variety of skill metrics of the user (e.g., as explicitly provided by the user or implicitly determined based on a user's interaction with content items). Advantageously, such metrics can enable generation of recommendations based on a multi-dimensional difficulty assessment. Further, difficulty metrics, skill metrics, or the relationship between such metrics may be dynamically updated over time based on continued feedback from users, such that recommendations are dynamically improved.