O

OAI-PMH : Open Archives Initiative Protocol for Metadata Harvesting

OAIster

OAPEN : Open Access Publishing in European Networks

OATD : Open Access Theses and Dissertations

Obra huérfana

Oceanic Abstratcs

OCR : Optical Character Recognition

OCLC : Online Computer Library Center

OCW : OpenCourseWare

OER Commons

Offsetting

OJS : Open Journal System

OPAC : Catálogo Público de Acceso en Línea

OpenDOAR

OpenAIRE

ORCID : Open Research and Contributor ID

ORE : Open Research Europe

Osiris