Merkle, R.K.W. (Roland Karl Willi), 1954-2022-01-122022-01-122021/05/062020*A2021http://hdl.handle.net/2263/83200Thesis (PhD)--University of Pretoria, 2020.en© 2021 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.UCTDThesis