3 different sources that I have found:
Books
1. MacEachern, Diane. Big Green Purse. Use Your Spending Power To Create A Cleaner, Greener World. New York. 2008.
In this book, it is more related to our environment problem. So we can get the suggestion of some simple environment lifestyle changes in our cleaning industry.
2. Tan, Chwee Huat. Employment Relations in Singapore. Singapore: Prentice Hall, 1999.
This book covers the major issues in employment relations in Singapore. It is written mainly for students who need to know the basic issues of them. It also included the environment within the employment relations operate and the changing features of the labor force.
Magazines/ Newspaper
3. Seow, Joanna. "Labour movement launched campaign to appreciate workers, starting with cleaners" The Straits Time. 16 Jun 2014
<http://www.straitstimes.com/singapore/labour-movement-launches-campaign-to-appreciate-workers-starting-with-cleaners>
4. Li, Xueying, and Suhaimi, Nur Dianah. "Not-s0-golden years for the elderly in Singapore ". The Straits Time. 23 Aug 2010
<https://www.healthxchange.com.sg/News/Pages/Not-so-golden-years-for-the-elderly-in-Singapore.aspx>
Online Sites
5. 'Why are there so many old people working in hawker centers in Singapore? I noticed some old people cleaning tables who are having a hard time walking'. Wikisource. Accessed 28 Sep 2014.
<https://www.quora.com/Why-are-there-so-many-old-people-working-in-hawker-centers-in-Singapore-I-noticed-some-old-people-cleaning-tables-who-are-having-a-hard-time-walking>
6. Ng, Kok-Hoe. 'Review Essay: Prospects for Old-Age Income Security
in Hong Kong and Singapore'. Published online 26 Nov 2011.
<http://tsaofoundation.org/doc/old_age_income_security.pdf>
About Tay Kheng Soon
Principal Partner of Akitek Tenggara within Singapore & Malaysia
Tay Kheng Soon has been a professional architect since 1964. He was chairman of Singapore Planning and Urban Research Group ( SPUR ) in 1970. SPUR was an independent group examining urban environment and was active in proposing innovative solutions. He was President of the Singapore Institute of Architects from 1991 - 1993.
His professional activities included a specialization in high density, low rise, low-cost housing in Malaysia. He did pioneering work in commercial centres and shopping centres in the 70's. Currently he is involved in educational and community projects throughout South-East Asia.
His public contributions have been as Chairman of the Task Force for the Long-term Development of the Singapore National Museum, Chairman of the Committee on Heritage for the Singapore Advisory Council on Culture and the Arts. He was also Founding Chairman of The Substation, a cutting-edge arts centre. His civic activities include being a member of the Advisory Panel of the Government Parliamentary Committee on National Development and a member of the advisory panel of the Singapore Institute of Policy Studies. He has been appointed in 1997 Adjunct Professor of Architecture at RMIT of Australia. He was appointed in 1998 Adjunct Associate Professor MA(UD) program National University of Singapore.
His academic involvements included being a Visitor Scholar under the Aga Khan Program at MIT in 1986 and in 1989. He was also Research Fellow with the Institute of Southeast Asian Studies (ISEAS) and published a monograph, 'Mega-cities in the tropics'. The monograph began a series of papers on sustainable mega-cities in the tropics. This activity led to appointment to prepare a development guide plan for a fringe urban site in Singapore where he proposed 'the Tropical City Concept'
The book, "Line, Edge and Shade" by Robert Powell on his writing and work and that of Akitek Tenggara was released in June 1997.
He is a member of the prestigious World Academy of Art and Science and was awarded the Singapore Institute of Architects Gold Medal in 2010.
Sources: http://www.rubanisation.org/index.php?option=com_content&view=article&id=57&Itemid=29