Repeat the reference when switching between different sources so that it is clear what source is connected to the given information. Read your sentences carefully to ensure you have cited the sources appropriately and that it is clear to the reader. 

Example: 

Fox (2010) claims that reading aloud surely can be regarded as a teaching situation. When children and adults are gathered around a book, the child's communication skills are reinforced. (Dominkovic et al., 2006). Moreover, it helps the child to learn to relax and it also increases the child's ability to concentrate (Fox, 2010). 

If you refer to several works at the same time, they are stated in alphabetical order by the author and then in chronological order. Semicolons are used between each reference. The order is then the same as in the reference list and it is easy for the reader to find them. 

• Man's eternal dream of conquering space is manifested in many different ways (Eco, 2005; Johansson, 2006; Thulin, 2000, 2004)
• Meurling talks about gender roles and ideals of beauty (1999, 2003)

Read more on APA-Style: Citing multiple works