The phrase "a topic touched upon" is correct and usable in written English.
It can be used when referring to a subject that has been briefly mentioned or discussed in a conversation or text.
Example: "In the meeting, several important issues were raised, but the topic touched upon was the need for better communication within the team."
Alternatives: "a subject mentioned" or "a point addressed".
Topics touched upon by the symposium's panels ranged from institutional prejudice to the masculinity entrenched in the stories told on stage.
The copious topics touched upon include "that gobshite" Jimmy Savile, Nelson Mandela ("I never thought somethin' as ordinary as watchin' someone goin' for a walk could be so incredible") and heavy drinking ("I'd need three pints before I decide whether to go on a fuckin' binge or not").
My latest presentation on the website of the Asociación Rural del Paraguay given recently at the 4º Congreso Ganadero in Asunción contains further explanations and illustrations on the topics touched upon herein (http://www.arp.org.py/index.php?option=com_content&view=article&id=841, http://www.arp.org.py/images/files/Ganaderia%20y%20ALBRECHT%20GLATZLE.pdf%20ALBRECHT%20GLATZLE.pdf
Other subjects and topics touched upon include science, art, culture, natural history, superstitions, and psychology.
If you're looking for more information on the topics touched upon above, I've found The Alliance of Suicide Prevention Charities website helpful in the past.
This week the singer was forced to defend accusations that the Born This Way foundation had spent more than $1m on legal fees, consulting and publicity, although this topic wasn't touched upon during the keynote speech.
It is not as if the topic has only been touched upon, Stevens said.
The topic was also recently touched upon by Heino et al. (2013) who argued that FIE might at least initially increase per capita population growth rates.
Because the manager had a coordinating role, the topic list touched upon multiple aspects of the implementation process including recruiting and training the lifestyle counselors, instructing the OPs and medical assistants, overseeing OPs and medical assistants who select and refer employees, and planning counseling sessions.
The first hypothesis, that the published abstracts contain all pertinent findings, does not exclude radiation exposure as a topic to be touched upon in the contribution but is not expressively mentioned in the abstract.
