Standard references

Please refer to these standard references for Spanish.
1. Real Academia Española: https://www.rae.es/
2. Fundación del Español Urgente: https://www.fundeu.es/

Other good sources

3. Diccionario panhispánico de dudas: https://www.rae.es/dpd/
4. RAE - Manual de la Nueva Gramática de la Lengua Española: https://drive.google.com/file/d/0B8BiCoxC6OQ1LWFEbU9TMDZ4OHc/edit?resourcek ey=0-mNua1ai9c-7BXixbLXySXQ
5. Longman Dictionary of Contemporary English: https://www.ldoceonline.com
6. Microsoft Language Portal: https://www.microsoft.com/es-es/language
7. ProZ: https://www.proz.com/search
8. UNTERM Terminology: https://unterm.un.org/unterm/portal/welcome
9. IATE: https://iate.europa.eu/home

NEXT TOPIC ⇒STYLE AND TONE