Related to arXiv.  A lot of technical information about the system, not much else.

Can be browsed online via the Vocabulary Bank for Education but interface is complicated so probably better to download.

Will be translated into more languages. "The complete thesaurus, or any substantial part of the thesaurus, may not be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the permission of the copyright holder."