In this paper we propose Arcomo, a mobile learning environment designed for hybrid wireless networks. We introduce three key concepts used in the environment: spaces,anchor points, and artefacts. Spaces are used to uniquely identify, store, share, and disseminate learning materials, annotations, and examples among mobile users. Anchor points are defined by users on documents in spaces. Every anchor point specifies a location in a document, whichcan be a word, a sentence, a paragraph, an image, or even the whole document. Artefacts are utilized to describe relationships between anchor points together with comments on them. This way, they can map the current working context of a student that typically contains several open documents and a relationship between them. The main contribution is a general annotation concept which supports different file formats and is applicable for collaborative mobile users.