If you're interested of learning more about ASN.1, two great books on the subject are:
- ASN.1 Communication between Heterogeneous Systems[0]
- ASN.1 Complete[1]
Both of which are available online for free. Last time I checked, they may not cover the latest fads like JER etc. but will provide you with a solid understanding of ASN.1 nonetheless.
All standards about ASN.1 (not including standards that use ASN.1 like MMS) are available for free from the ITU under the X.680 to X.697 series of standards.[0]
- ASN.1 Communication between Heterogeneous Systems[0]
- ASN.1 Complete[1]
Both of which are available online for free. Last time I checked, they may not cover the latest fads like JER etc. but will provide you with a solid understanding of ASN.1 nonetheless.
[0] https://www.oss.com/asn1/resources/books-whitepapers-pubs/la... [1] https://www.oss.com/asn1/resources/books-whitepapers-pubs/du...