Fits mixtures of multivariate contaminated normal distributions
        (with eigen-decomposed scale matrices) via the expectation conditional-
	maximization algorithm under a clustering or classification paradigm
	Methods are described in Antonio Punzo, Angelo Mazza, and Paul D McNicholas (2018) <doi:10.18637/jss.v085.i10>.

Provides methods for difference-in-differences with a continuous treatment and staggered treatment adoption. Includes estimation of treatment effects and causal responses as a function of the dose, event studies indexed by length of exposure to the treatment, and aggregation into overall average effects. Uniform inference procedures are included, along with both parametric and nonparametric models for treatment effects. The methods are based on Callaway, Goodman-Bacon, and Sant'Anna (2025) <doi:10.48550/arXiv.2107.02637>.

Provides comprehensive tools for extracting and analyzing scientific 
    content from PDF documents, including citation extraction, reference matching, 
    text analysis, and bibliometric indicators. Supports multi-column PDF layouts,
    'CrossRef' API <https://www.crossref.org/documentation/retrieve-metadata/rest-api/> integration, and advanced citation parsing.

An interface for creating, registering, and resolving content-based
             identifiers for data management. Content-based identifiers rely on
             the 'cryptographic' hashes to refer to the files they identify, thus,
             anyone possessing the file can compute the identifier using a 
             well-known standard algorithm, such as 'SHA256'.  By registering
             a URL at which the content is accessible to a public archive (such as 
             Hash Archive) or depositing data in a scientific repository such 'Zenodo',
             'DataONE' or 'SoftwareHeritage', the content identifier can serve 
             many functions typically associated with A Digital Object Identifier
             ('DOI').  Unlike location-based identifiers like 'DOIs', content-based
             identifiers permit the same content to be registered in many locations.