Standard abbreviations for polycyclic aromatic hydrocarbons, similar to those for nucleic and amino acids?

The Nature paper [Characterizing particulate polycyclic aromatic hydrocarbon emissions from diesel vehicles using a portable emissions measurement system](https://www.nature.com/articles/s41598-017-09822-w) addresses polycyclic aromatic hydrocarbons (p-PAHs) and both the text and the plot below make extended use of *short, mixed-case abbreviations* for various specific p-PAHs.


**Question:** Do these refer to some standardized naming convention for p-PAHs? If so, where can this be found?




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[![polycyclic aromatic hydrocarbons histogram](https://i.stack.imgur.com/gu7hJ.jpg)](https://i.stack.imgur.com/gu7hJ.jpg)



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> Figure 2. Average distance-based emission factors for each p-PAH component according to the engine type.
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(electronically-controlled fuel injection (EI) and mechanical pump fuel injection (MI))




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For amino acids and nucleic acids for example, standard one- and three-letter abbreviations exist:


* [Table of standard amino acid abbreviations and properties](https://en.wikipedia.org/wiki/Amino_acid#Table_of_standard_amino_acid_abbreviations_and_properties)
* [Table of Amino Acids and Their Abbreviations](https://molbiol-tools.ca/Amino_acid_abbreviations.htm)
* [Nucleic acid notation](https://en.wikipedia.org/wiki/Nucleic_acid_notation)




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Here is an example of a plot where the abbreviations are not used. From Figure 20 of [polycyclic aromatic hydrocarbons in automotive exhaust emissions and fuels](https://www.concawe.eu/wp-content/uploads/2017/01/rpt_98-55-2004-01306-01-e.pdf):


[![polycyclic aromatic hydrocarbons histogram](https://i.stack.imgur.com/KD515.png)](https://i.stack.imgur.com/KD515.png)


