clarifications and fixes
diff --git a/README.md b/README.md
index 6f327c1..156b01b 100644
--- a/README.md
+++ b/README.md
@@ -11,13 +11,17 @@
<h1>How to build and install</h1>
-This code is intended to be distributed as a PostgreSQL extension on [PGXN site](https::/pgxn.org/)
+This code is intended to be distributed as a PostgreSQL extension on [PGXN site](https://pgxn.org/)
-This code is expected to be compatible with PostgreSQL versions 9.4 and higher. It was tested with REL_11_STABLE branch.
+This code is expected to be compatible with PostgreSQL versions 9.4 and higher. It was tested with REL\_11\_STABLE branch.
PostreSQL must be installed to compile the extension. The path to PostgreSQL executables must be set up (try running 'pg_config' to test).
This code requires C++11. It was tested with GCC 4.8.5 (standard in RedHat at the time of this writing), GCC 8.2.0, GCC 9.2.0, Apple LLVM version 10.0.1 (clang-1001.0.46.4) and version 11.0.0 (clang-1100.0.33.8).
+This code depends on [datasketches-cpp version 1.0.0-incubating](https://github.com/apache/incubator-datasketches-cpp/releases/tag/1.0.0-incubating)
+
+There are two slightly different ways to build this extension: from a PGXN distribution or from two separate packages: datasketches-postgresql and datasketches-cpp (either from GitHub or from [Apache archive](http://archive.apache.org/dist/incubator/datasketches/))
+
<h2>Building and installing PGXN extension</h2>
- Download the datasketches extension from [PGXN](https://pgxn.org/dist/datasketches/)
@@ -26,9 +30,9 @@
- sudo make install
- in the database console: create extension datasketches;
-<h2>Building and installing from source</h2>
+<h2>Building and installing from GitHub or Apache archive</h2>
- - Clone or download from GitHub, or download from Apache archive this datasketches-postgresql code and the core library datasketches-cpp
+ - Clone or download from GitHub, or download from Apache archive both the datasketches-postgresql code and the core library datasketches-cpp (version mentioned above)
- Place the core library as a subdirectory (or a link to it) inside of the datasketches-postgresql like so:
- datasketches-cpp
- datasketches-postgresql
