Sentence:  The four tones of Mandarin Chinese are often referred to conveniently in discourse by the numbers 1 to 4, and capital letters have been recruited to denote tones by <WSD>acrography</WSD> (H for high, M for mid, L for low, etc.), for example in ToBI notation (Tone and Break Indices; see Beckman and Ayers 1994), X-SAMPA notation (Extended Speech Assessment Methods Phonetic Alphabet; see Wells 1995b; and see Section 3.4.10 below) and INTSINT notation (International Transcription System for Intonation; see Hirst 2004). 
Meaning of the word marked with <WSD> tags:  An organizing principle for written lists, based on initial glyphs.