Refer to X.690 by number
It's easier to identify and find by number than by its very wordy
title, especially as there was a typo in the title.
/*
* Bit masks for each of the components of an ASN.1 tag as specified in
- * Information technnology - ASN.1 encoding rules: Specification of Basic
- * Encoding Rules (BER), Canonical Encoding Rules (CER), and Distinguished
- * encoding rules (DER) Section 8.1.2.2:
+ * ITU X.690 (08/2015), section 8.1 "General rules for encoding",
+ * paragraph 8.1.2.2:
*
* Bit 8 7 6 5 1
* +-------+-----+------------+
